The Committee on Climate Change (CCC) has said fracking can go ahead, if three key tests are met on methane leaks, gas consumption and carbon budgets.
The CCC’s report found that the implications of UK shale gas exploitation for greenhouse gas emissions are subject to considerable uncertainty – from the size of any future industry to the potential emissions footprint of shale gas production.
It also found exploitation of shale gas on a significant scale is not compatible with UK carbon budgets, or the 2050 commitment to reduce emissions by at least 80 per cent, unless the tests are satisfied.
The report said at this early stage, it is not possible to know whether the tests will be met easily or not and the Committee will closely monitor steps taken by Government and other relevant agencies to satisfy these tests.
The government says it already plans to meet those tests.
Professor Jim Skea, a member of the Committee on Climate Change, said: "Under best practice, UK shale gas may have a lower carbon footprint than much of the gas that we import.
"However, gas is a fossil fuel wherever it comes from and is not a low-carbon option, unless combined with carbon capture and storage."
Two sites,at Preston New Road and Roseacre Wood, were denied planning permission by Lancashire County Council last year.
A final decision on fracking at the sites in Lancashire is reported to be made by 6 October.
There have been various anti-fracking protests at the sites, including a 'Frack-Free Bake Off' attended by British actresses Emma and Sophie Thompson in April which resulted in legal action from landowners.