David Cameron is today accused of doing no more than pay lip service to his boast that he would lead the "greenest government ever" and of leaving Britain vulnerable to the economic and environmental dangers of failing to tackle climate change.

On the second anniversary of his speech setting out his "simple ambition" for the coalition, the Prime Minister comes under fire from business leaders, eco-campaigners and politicians who warn that ministers' anti-green rhetoric, policy U-turns and turbulent backbenchers are thwarting efforts to foster a low-carbon economy.

Samantha Smith, the environmentalist who took Mr Cameron to hug huskies in the Arctic to show a new Tory enthusiasm for the green agenda, leads the criticism. She claims the PM's reluctance to lead the way threatens investment in renewable energy and undermines attempts to persuade developing countries to go green.

She told The Independent on Sunday: "This where we see whether David Cameron is a global leader or not. It is about being out in front, showing leadership and direction. We are not seeing enough of that."

Her comments have been echoed by a diverse coalition, ranging from the CBI and renewable-energy firms to Greenpeace, Friends of the Earth and even Tory MPs.

From botched cuts to solar subsidies to the aborted forests sell-off, from a new rush for gas to subsidies for nuclear power, there is plenty in the coalition's record that has raised doubts about the competency and commitment of ministers to the cause.

Repeated attacks by George Osborne on low-carbon policies – claiming "we're not going to save the planet by putting our country out of business" – have been highlighted as a major cause of concern, with the Chancellor suggesting there is a choice between growth and being green.

The need for action remains acute. Last month, the International Energy Agency warned that energy-related CO2 emissions are on course to almost double by 2050, pushing global temperatures up by at least 6C. "Such an outcome would confront future generations with significant economic, environmental and energy security hardships," said its deputy executive director, Richard H Jones.

Last Wednesday's Queen's Speech was seen by some as a turning point for the coalition. The Energy Bill will aim to provide long-term certainty for investors in low-carbon power, by guaranteeing a steady rate of return. But critics warn it amounts to a subsidy for nuclear plants, something Lib Dems are vehemently opposed to. The heads of four of the country's biggest environmental organisations – Greenpeace, WWF, RSPB and Friends of the Earth – have written to the Government warning against an "over-reliance on gas", which could account for 70 per cent of generating capacity by 2020. The letter, seen by The IoS, calls for more support for renewable energy to "provide investors with long-term certainty".

Ultra-green members of the Government would like more "aggressive" policies, including council tax and business rate discounts for properties that are more energy-efficient. But these are unlikely to get past sceptics who would see it as another "green tax".

Earlier this month, Mr Cameron made his first public comment on the green agenda since becoming Prime Minister, though confusion over whether it was a "keynote speech" or simply "opening remarks" at a meeting of international energy ministers added to the sense that this is not a policy priority. A YouGov poll in March revealed that just 2 per cent of people thought he had kept his promise to lead the greenest government ever.

It is all a long way from the day in April 2006, when Mr Cameron burnished his green credentials by posing with huskies in Svalbard, declaring: "It is possible to take a lead and make a difference."

Six years on, it is the absence of leadership that most worries environmentalists. Ms Smith, now leader of WWF's global climate and energy initiative, revealed she was "impressed" by the Tory leader on the infamous dog-sled trip, but today is fearful of a lack of conviction. "We understood that part of it was about promoting the new greening of the Tory party, but it also seemed to us to be genuine, beyond some false commitment and a nod to climate change." She warns that Mr Cameron must stand up to the "huge pushback" claims from climate-sceptic Tory MPs and Mr Osborne, who express doubts "on whether the UK can 'afford' to fulfil its obligations".

There is a stark difference between being the "greenest ever" and the "greenest possible" government. Without a pro-green zeal at the very top of government, ambitious plans are unlikely to reach their potential. "It's the difference between a policy that trundles along and one which is given some welly," says one government source.

Like many, Tim Yeo, the Tory chairman of the Commons Energy and Climate Change Committee, warns that the Department of Energy and Climate Change looks like "a second-division Whitehall department" when up against the Treasury, which is institutionally suspicious of green policies. The Department for Environment, Food and Rural Affairs fares little better. Responsible for the countryside – and the infamous plan to sell off Britain's forests – it is damned with faint praise even by its backers. "Defra's heart is in the right place," says one. "It just needs a bit more clout." The Campaign to Protect Rural England fears Defra is "an isolated, and not especially influential, outpost".

The loss of Chris Huhne, who resigned as Energy Secretary in February after being charged with perverting the course of justice, is a mixed blessing. A Lib Dem big beast, he regularly stood up to Tories in general and Mr Osborne in particular. But there is a growing school of thought in Westminster, too, that Mr Huhne's spiky relationship with the Chancellor was counterproductive. Friends of Mr Osborne say his anti-green rhetoric while Mr Huhne was in the Cabinet was in part a way of putting up "two fingers" to the Lib Dems. Since the latter's departure, his language has been tempered. "George has drawn a line under the antagonistic stuff now Chris has gone," says one Tory minister. "Politics is based on people and relationships – shock!" adds another.

Observers say the jury is still out on Mr Huhne's successor, Ed Davey. In his first interview after his appointment in March, Mr Davey told The IoS: "Let no one be under any illusion, I am completely committed to the ambition for this to be the greenest government ever."

He might be committed. But there are real doubts about whether David Cameron's priorities now lie far away from the glaciers of Svalbard.

Cameron's Green ratings (are all over the place)

Leadership

David Cameron's "greenest government ever" boast on 14 May 2010 was followed by almost two years of silence. George Osborne filled the void, claiming green regulations imposed a "ridiculous cost" on business. The loss of Chris Huhne as Energy Secretary leaves both the Lib Dems and the green lobby one big beast down. But William Hague boasts that the Foreign Office is "leading this charge with vigour" and Nick Clegg is to lead the UK delegation to the Rio Earth Summit.

Verdict Sometimes words speak louder than actions.

Economy

The low-carbon economy, employing one million people, has been growing by 4 per cent a year, despite the recession. The UK is ranked seventh in the world for investment in clean energy, which was $9.4bn in 2011 – up 35 per cent, from $7bn, on 2010. Business leaders dispute claims about the green "burden", but want consistency to reassure investors. The £3bn Green Investment Bank, to fund low-carbon energy schemes, will start lending this year, though critics note it won't be able to borrow until 2016 at the earliest.

Verdict Treasury blind to potential green shoots of growth.

Solar

Panicked by the high uptake of generous subsidies for people installing solar panels, the Government rushed to cut the payouts by half. The High Court blocked the move, which had triggered claims that manufacturers and installers would go bust, and set alarm bells ringing about ministers' commitment and competence.

Verdict Cock-up, not conspiracy, but investors spooked.

Wind

More than 100 Tory MPs demanded cuts to subsidies for "inefficient and intermittent" onshore wind farms, but the PM responded there were "perfectly hard-headed reasons" to build more. There are plans for big expansion by 2020, pushing onshore turbine output up from 4.7GW to 13GW and offshore from 1.6GW to 18GW.

Verdict "Bird shredders" or things of beauty, they are vital to green energy future.

Marine and tidal

Coalition pulled the plug on Severn Barrage, but has a target for 200MW to 300MW of marine capacity by 2020. However, a £20m fund is a drop in the ocean for a technology still in its infancy.

Verdict A lack of vision means the sector could sink.

Energy efficiency

The Green Deal, offering homes lagging, boilers and low-energy lights paid for through future savings on bills, is seriously ambitious – hoping to stimulate £14bn-worth of private funding – but it has real potential to go wrong and risks low take-up. Smart meters, giving live updates on energy use, rolled out by 2019.

Verdict Big, bold thinking but could be a damp squib.

Carbon emissions

The fourth carbon budget promises to halve carbon emissions, from 1990 levels, by 2025. The UK government is leading the argument in Europe to go for a 30 per cent cut in emissions by 2020, up from 20 per cent. Government departments cut emissions by 14 per cent in the coalition's first year. Plans for a carbon capture and storage project in Fife, Scotland, were scrapped but a £1bn fund has been made available to help this burgeoning technology.

Verdict Ambitious targets require ambitious politicians.

Countryside

A plan to sell off half the Forestry Commission's woodland was ditched after a campaign attracted 500,000 signatures. A planning shake-up sparked fears the countryside would be concreted over before a partial climbdown. An injection of £250m to reinstate weekly bin collections contradicts the recycling message. But a Defra review of habitat directives showed just 0.5 per cent caused major problems. There are plans to plant one million trees by 2015.

Verdict The rural champion risks trampling on its grassroots.

Oil and gas

A £3bn tax break in March to help oil firms to drill new deep wells off the north of Scotland dismayed campaigners, coming 12 months after a £2bn increase in tax on oil production. The requirement for power stations to be more efficient and less polluting is to be scrapped. Critics warn it will lead to a new dash for gas. Fracking – pumping water into shale rock to release gas – remains controversial, including fears it causes tremors.

Verdict No sign of ending our addiction to the black stuff.

Airports

The PM promised to scrap plans for a third runway at Heathrow, but the Chancellor is pushing for a U-turn, telling MPs the country must "confront airport capacity in the South-east".

Verdict A U-turn after the 2015 election would retoxify the Tories.

The experts' view

"Treasury noises-off are not helpful. A lot of this is work in progress but more signs are encouraging than discouraging."

Tim Yeo, MP; Tory chairman, Commons Energy and Climate Change Committee

"The Government's record is good in parts. They say the proof is in the pudding, well the pudding is still in the oven."

Gordon Edge; Policy director, RenewableUK

"It's more subtle than saying it's all been terrible – but it's more tragic, as well, because they have the bits of the jigsaw."

Caroline Lucas, MP; Leader, Green Party

"The economic climate has made politicians less receptive to the green agenda, but the 'environment vs growth' argument is self-defeating. This Government can still be the greenest ever, but it needs to raise its game."

Ben Stafford; Head of campaigns, Campaign to Protect Rural England

"The real issue is whether the 'greenest government ever' was a genuine aim, a sop to the Lib Dems, or a PR slogan."

Joan Walley, MP; Labour chairwoman, Commons Environmental Audit Committee

"The Government has caved into fossil-fuel lobbyists and green-lighted a risky increase in our dependence upon imported, polluting gas."

Joss Garman; Senior campaigner, Greenpeace

"The chopping and changing of green policies has been damaging to business confidence. The Government must ensure it has a clear message."

Rhian Kelly; Director for business environment, CBI

"We need to ensure more advanced engineering and manufacturing to create the solutions that will be essential to meeting our climate-change goals."

Greg Barker, MP; Climate Change minister

"David Cameron's pledge to vote blue and go green was nothing more than a con, designed to trick people into thinking the Tories had changed."

Caroline Flint, MP; Labour climate change spokeswoman

"The 'greenest government ever' aspiration was hardly setting the bar high, so it's a let-down to see the Government struggle to rise to that standard."