The government has reversed its decision to accept new fracking restrictions, meaning shale gas firms will be able to drill horizontally under National Parks, provided the wells start outside their borders.

MPs were forced by backbenchers to accept new fracking regulations in January, which included avoiding fracking in Areas of Outstanding Natural Beauty (AONB) and National Parks, but final amendments to the regulations unpicked some of the finer details.

Having welcomed the new regulations at the time, Green MP Caroline Lucas said ministers were “doing the dirty work of the fracking companies for them.”

Other regulations passed by MPs included a ban of fracking in sites of scientific interest and groundwater source protection zones, which analysts said could rule out 40 percent of the UK land offered by the government for shale gas exploration.

But following amendments, Energy and Climate Change Minister Amber Rudd told MPs it would be impractical to guarantee a fracking ban in some rural areas.

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“In the case of AONBs and national parks, given their size and dispersion, it might not be practical to guarantee that fracking will not take place under them in all cases without unduly constraining the industry.”

She added that putting strict measures in place would hinder shale gas goals.

“We must not rush this now, because we would risk putting in place restrictions in areas in a way that does not achieve the intended aim, or that goes beyond it and needlessly damages the potential development of the shale industry.”

Prime Minister David Cameron has previously said the government is “going all out” for shale to create jobs and decrease reliance on oil-producing countries, but opposition groups believe unregulated fracking will cause damage to the environment and public health and prevent the country from meeting its climate change goals.

The amendments were met with anger from Labour Party ministers, whose Shadow Energy Minister Tom Greatrex said fracking under protected areas could mean they would be hemmed in by shale gas operators.

“The range of protections [accepted by the government in January] cannot be cherry-picked. It is vital for groundwater, and sources of drinking water, to be properly protected.”

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He further accused MPs of endangering public health by going back on the decision to that Health and Safety Executive inspections on drilling sites would be unannounced.

The Labour party says it will continue to push for restrictions on fracking if it wins the general election.

Green Party MP and staunch anti-fracking campaigner Caroline Lucas called the amendments and limited time scheduled for debate a “mockery.”

“What a mockery this is making of legitimate public concerns on fracking, and indeed of the democratic process.”

Shale companies, however, welcomed the decision.

The CEO of trade body UK Onshore Oil and Gas, Ken Cronin, said the move would allow companies to continue to explore potential drilling sites.

“The industry can get on with finding out the extent of the recoverable reserves of natural gas below our feet. Many of the issues raised in the amendments are already complied with by the industry voluntarily.”