The Government has been accused of lobbying Europe to water down efforts on tackling climate change, ahead of the publication of proposed EU carbon cutting targets for 2030.
The European Commission will this week set out proposed targets for EU-wide carbon emissions reductions by 2030 as part of a package of climate measures.
A series of targets are in place up to 2020, including reducing Europe's emissions by 20% on 1990 levels and sourcing 20% of energy from renewables.
But in the face of lobbying from the UK Government, the Commission could fail to set new targets for cleaning up transport fuel used in the EU - effectively opening the door for polluting "tar sands" produced in Canada to enter the bloc.
Green groups are also concerned the Commission will not set out binding targets for producing more energy from renewables up to 2030.
And it is likely to publish a series of recommendations for developing shale gas projects in member states, rather than drawing up new EU-wide regulations on fracking.
The UK opposes a renewables target for 2030, arguing it would stop countries using the most cost-effective ways of cutting emissions, which could include non-renewable technology such as nuclear power and measures to cut carbon from conventional power stations.
The Government, which has gone "all out" for shale, has also warned against new legislation on fracking which could delay investment or create uncertainty for the new industry in Europe.
And the UK has argued against setting new targets for cutting emissions from transport fuels under the fuel quality directive after 2020.
The directive demands a 6% cut in emissions from transport fuel by 2020, and efforts have been made to class tar sands as more polluting than conventional oil, which would effectively stop its import to EU countries.
But abandoning targets for the fuel quality directive after 2020 would undermine efforts to reduce emissions from transport fuels this decade and beyond, and open the door to tar sands coming into Europe, including the UK, environmentalists say.
Analysis out this week from the Natural Resources Defence Council suggests without action to stop it, almost 7% of crude oil and transport fuel Europe uses could come from imported tar sands, as Canada seeks to find a new market in the face of an oil glut in the US pushing up EU transport fuel emissions by 1.5% .
Dr Doug Parr, Greenpeace's chief scientist said: "Keeping down emissions from the production of transport fuels is a critical part of a European decarbonisation drive and the failure to include relevant targets in the 2030 framework, together with the foot-dragging over the existing targets, would fire the starting gun on a rush of some of the dirtiest fuels imaginable, like tar sands, flowing into Europe.
"The UK have played a dirty game in getting the Commission to abandon any post 2020 targets restricting and keeping out filthy fuels like tar sands from the EU market.
"Taken with their irrational and religious enthusiasm for shale gas, rolling back on green measures at home and weakening of European efficiency standards it seems like the UK is more of a fossil-fuel junkie than the greenest government ever."
Greenpeace executive director John Sauven added: "The weak, non-binding target on renewables the UK Government has lobbied for would be nothing short of a stab in the back for the clean energy sector.
"Only a binding target will give investors the clear signal they've been waiting for, helping drive down the costs of renewable energy, creating more green jobs, and giving a boost to the UK economy."
The UK Government has argued for ambitious targets to cut EU emissions by 2030, with a binding greenhouse gas reduction of 40% by the end of the next decade, which could increase to 50% if there was a global deal on tackling climate change.
Earlier this month, the UK joined with Germany, Italy and France to urge the Commission to include a binding EU greenhouse gas emissions reduction target of at least 40%.
But a spokesman for the Department of Energy and Climate Change said: "It makes no sense to impose artificial constraints on how individual countries meet emissions targets.
"We are determined to keep people's energy bills as low as possible and that means having the flexibility to cut emissions in the most cost effective way."
In a letter to European Commission president Jose Manuel Barroso last year, Prime Minister David Cameron claimed a renewable energy target for 2030 could add up to £9 billion on UK bills, though it is not clear where the figure has come from.
Countries including France, Germany, Ireland, Italy and Portugal have called for a renewable energy target in the 2030 package.
The Commission is set to publish its 2030 white paper and other measures on Wednesday.