Public support for fracking for shale gas in the UK has fallen below 50% for the first time, new polling suggests.

Just 49.7% of people now say they think the controversial process should be allowed in the UK, marking the third fall in support since high-profile protests last summer in West Sussex which saw dozens of arrests including that of Green MP, Caroline Lucas and ongoing protests at a site in Salford.

Support for shale gas was at a high of 58% in July 2012, which slumped to 54% last September and 53.3% this January, the long-running survey by YouGov for the University of Nottingham shows.

Last week, the Tory peer Lord Howell, who is chancellor George Osborne's father-in-law and who caused a furore last year when he said fracking should take place in the "desolate" north-east, warned that fracking could cost the Conservative party electorally.

"Every time ministers open their mouths to claim that fracking must start everywhere around Britain, and not just in carefully selected and remote (derelict) areas, they lose thousands of Tory votes," he wrote in an article for the US-based Journal of Energy Security.

Public attitudes towards fracking for shale gas appear to be increasingly polarising along political lines.

The University of Nottingham poll shows Labour voters have gone from a high of 52% in favour to 41% now. Tory voters have been consistently high in their support for exploiting shale gas, with 67% in favour, which is broadly similar to Ukip voters.