Over 200 pubs across Britain have been converted into supermarket branches since January 2010, according to figures published by the Campaign for Real Ale (Camra), while a further 45 are under threat.

Camra said "weak" and "misguided" planning laws have enabled the UK's biggest supermarkets to "rip the hearts of out small communities" by converting pubs into shops such as Tesco Metro or Sainsbury's Local.

The group is stepping up its campaign to persuade the government to close legal loopholes in England and Wales that allow pubs to be demolished or converted without the need for planning permission. It says communities have been rendered "powerless" in the fight to save their locals.

Using figures based on a national pub conversion survey carried out by its members, Camra found that since the beginning of 2010, 130 pubs have been converted into stores by market leader Tesco alone. A further 22 have been converted by Sainsbury's, and 54 by other companies such as The Co-operative, Asda and Costcutter.

Critics say a legal loophole allows pubs to be converted to mini-markets without planning permission, leaving councils powerless to halt the process.

The legal position is that the building as it stands (ie, former pub) can be used for retail without the need for fresh planning permission – as a pub is effectively already a retail outlet. As long as the floor space is no more than 280 sq metres (3,000 sq ft), the retailer can bypass the Sunday Trading Act and remain open all hours.

Mike Benner, the chief executive of Camra, said: "Weak and misguided planning laws and the predatory acquisition of valued pub sites by large supermarket chains, coupled with the willingness of pub owners to cash in and sell for development, are some of the biggest threats to the future of Britain's social fabric.

"For years, large supermarket chains have shown a disregard for the wellbeing of local communities, gutting much-loved former pubs in areas already bursting with supermarket stores.

"At a time when 18 pubs are closing every week this is damaging a great British institution. Unless action is taken by the government to address obvious loopholes in planning legislation, more local communities will be forced to give up their local pub without a fight, and seeing the pub signs of Red Lions and Royal Oaks being corporately graffitied over by supermarket empires will become an all-too-common sight."

Tesco said it had no policy of specifically targeting pubs. Its community director, Michael Kissman, said: "We are part of the solution, not the problem. We are taking on derelict or vandalised pubs, not those which are still actively trading, and for all sorts of reasons those pubs were not successful. We go into communities and ask people what they want and how we can deliver that."

John Denham, Labour MP for Southampton Itchen, added: "Residents across the country are feeling powerless to intervene as local community pubs are being turned into convenience stores. The Castle, a pub in my own constituency in Southampton, is the latest in a line of pubs being sold by large pub company, Enterprise Inns, to the giant supermarket chain Tesco."

He said the government needed "to wake up to this looming crisis in the pub industry" and urged it to look "not only at planning laws that allow pubs to be converted so easily, but also at the cosy relationship between national retailers and large pub companies that so often leave local communities feeling left out in the cold".

A Camra spokesman said that based on official correspondence it has received, and discussions in parliament, "the government is unconvinced that further controls over change in use are necessary, and has also passed the buck on to local authorities saying they have the powers to remove these deemed planning permissions locally".