The lobbying industry has tried to clean up its act since 1998's cash-for-access scandal, which saw Peter Mandelson's spin doctor Derek Draper fired over his links with lobbyists, but it remains controversial.

The Hansard Society last week launched an investigation into the role of lobbyists, under the title Friend or Foe?, questioning their influence on British democracy and asking whether they can be trusted.

Lobbyists working for the nuclear industry, which employs 40,000 people in the UK, have always been well-funded, but since the 1986 Chernobyl disaster were widely assumed to be fighting a losing battle.

Sophisticated campaign

But as the debate about Britain's future energy needs has intensified, the industry's reputation has been rehabilitated, with Labour politicians at least.

"There has been a very sophisticated public relations campaign by the nuclear industry, using climate change, using energy security, saying that nuclear is now cheap and safe, and a few years ago the technology was dead in the water," says Andy Rowell of Greenpeace-funded Nuclear Spin website.

There are certainly no shortage of links between the nuclear industry and the New Labour establishment.

Since 2004, BNFL, the government-owned nuclear reactor operator, has used lobbyists Weber Shandwick to help it push the case for new nuclear plants.

Fast-track planning

Weber Shandwick's UK arm is headed by Colin Byrne, the Labour Party's former chief press officer and an ex-spin doctor for Prince Charles.

French energy giant EDF has also been at the forefront of the campaign to change perceptions of nuclear power.

The company, which operates 58 nuclear reactors in France and is already a big player in the UK electricity market, has said it is ready to invest in a new generation of plants in the UK, provided it gets the go-ahead from government.

It has successfully lobbied ministers to introduce a fast-track planning process to make it easier to build new plants without lengthy public enquiries.

Chancellor Gordon Brown's brother, Andrew, is EDF's head of media relations in the UK.

One of the most well-connected nuclear lobbyists is Alan Donnelly, former leader of the Labour group in the European Parliament.

Mr Donnelly's company, Sovereign Strategy, represents US engineering giant Fluor, one of the world's biggest nuclear contractors, which is currently vying for a slice of the UK's £70bn nuclear clean-up market - but like other US firms, such as Bechtel, also has an eye on future nuclear build.

Kitchen row

On its website, Sovereign Strategy, offers among other services, "pathways to the decision makers in national governments".

Its board members include Tory peer Lady Maitland and pro-nuclear Labour peer Lord Cunningham, Tony Blair's former "cabinet enforcer" and the ex chairman of the Friends of Sellafield campaign.

Lord Cunningham is also "legislative chair" of the Transatlantic Nuclear Energy Forum, an organisation founded and run by Mr Donnelly, that aims to foster "strong relationships" between nuclear power companies and governments.

Tony Blair has spoken at events organised by Sovereign Strategy, including last year's North East Economic Forum in his Sedgefield constituency, where he was reportedly introduced by a Fluor executive.

But it is Mr Donnelly's links with environment minister David Miliband which created a stir earlier this year, when the Sunday Times ran a story about the lobbyist paying £2,000 towards the refurbishment of Mr Miliband's constituency office.

Mr Donnelly insisted he was acting in his capacity as the chairman of Mr Miliband's constituency Labour Party in South Shields. Both men have firmly denied any impropriety.

Writing in the July edition of Public Affairs News, Mr Donnelly said the money had been declared - and he had given it because he has been a Labour Party member for 32 years "and the party workers needed the kitchen fixing".

He wrote: "The crux of the story was this: That David Miliband would be so ecstatic with the £2,000 spent on his constituency kitchen that, were he fortunate enough to become environment secretary one day, he'd pull out all the stops to award one of our clients the contract to build a whole raft of nuclear power stations.

"It was nonsense, but that's the way it goes."

Peers' payment

Sovereign Strategy has also been criticised by the Association of Professional Political Consultants (APPC) - of which it is not a member - for having parliamentarians on its payroll, something the trade body prohibits in its code of conduct.

"We pay them for their work because they deserve to be paid for their time," Mr Donnelly wrote of the two peers who sit on his board.

He insists Sovereign takes its ethical responsibilities "very seriously", refusing to get involved in the running of cross-party parliamentary groups - some of which have accepted funds from lobbyists - as this "lacks transparency".

He also defends his company's donations to the Labour Party which, he says, are "not on a 'cash-for-coronets' scale" and says that his company is not the only lobbyist to have funded the party.

Lobbyists such as Sovereign and Weber Shandwick rely on their contacts in the corridors of power to impress potential clients and bring in new business.

Green lobby

But how much influence do they actually wield over government policy?

And what about the role of the anti-nuclear lobby - groups such as Greenpeace and Friends of the Earth - less well-funded, perhaps, but arguably no less well-connected, and with a canny knack for grabbing headlines?

There are many links between the government and the green lobby - although several former advisers are now firmly opposed to its policies.

Greenpeace executive director Stephen Tindale, a former special adviser to Labour ministers Chris Smith and Michael Meacher, has been highly critical of the government's nuclear policy.

Stephen Hale, director of the Green Alliance, who was a special adviser to Margaret Beckett when she was environment secretary, has also attacked what he called Tony Blair's "obsession" with nuclear power.

And the government's independent Sustainable Development Commission, chaired by ex-Friends of the Earth chief Jonathan Porritt, has also been sceptical about nuclear.

'Old boy network'

Because it is made up of voluntary organisations or charities, the green lobby can claim to have a certain amount of public support, which can help open doors in Whitehall.

But it is not enough for green campaigners just to be seen as "nice people", argues Greenpeace's Jean McSorely - they must also have the stronger arguments.

The pro-nuclear lobby has been clever in using environmental arguments, on climate change, and the security of supply issue, to push its case, she says.

She believes Greenpeace has a stronger scientific case, but, she argues, it does not always get a fair chance to make it.

"The access industry gets is just phenomenal compared to green groups," she tells the BBC News website.

"Labour has often castigated the old boy network, the public school tie and so on, but they have a similar network. It depends who you know in the unions or ex-Labour ministers.

"People may accept that as the way things are, but there needs to be more transparency."

Blair advisers

Having said that, she does not believe Mr Blair has been made to change his mind by the efforts of the pro-nuclear lobby - he was already a convert.

It was Mr Blair, she argues, who in 2003 insisted on the door being left open for nuclear in the government's energy white paper, which proposed a large increase in renewable energy.

"I don't believe Tony Blair has been influenced by lobbying. Both he and the industry have just been waiting for the right time to make their move", says Ms McSorely.

Where the lobbyists come in, she argues, is in "shoring up" support among other Cabinet ministers, MPs and the general public, and smoothing away potential opposition.

Industry voice

Mr Blair is thought to have made the decision to hold an energy review - potentially paving the way for the return of nuclear - after a meeting last September at Chequers with his advisers and representatives of the nuclear industry.

Those close to the debate believe it is these advisers - such as former BBC director general Lord Birt, industry adviser Geoffrey Norris and the government's chief scientific adviser Sir David King - who have most influenced the prime minister's thinking.

Insiders argue that Mr Blair is more than capable of making his own mind up based on the available evidence and the nuclear industry also rejects the suggestion it is given special access to ministers and other decision-makers.

With the industry employing 40,000 people in the UK, nuclear has a right to make its voice heard in government, argues John McNamara, of the Nuclear Industry Association.

He adds: "It should not come as a surprise that we do as much as we can to represent the interests of our industry, like any other large industrial sector."