The People's Supermarket was forced to defend its business at the ACS Summit this week after delegates branded it no different from any other retailer.

The member-owned co-operative opened in June last year, claiming it could compete on price with the multiples and give fairer prices to suppliers by saving on staff costs. Members must volunteer to work at the London store for at least four hours a month.

However, the concept came under attack at the ACS Summit, held this week in Birmingham, by Ewen Chisholm, COO of Scottish retailer David Sands. In a Q&A session, he told People's Supermarket joint founder David Barrie: "All you're doing is the job we're doing. You're just not paying your staff. There's virtually nothing there that we don't do."

Barrie was quick to defend the concept. "We want to be commercially competitive," he said. "If people choose to give their time to something they think there's value in, and they don't want to get paid, then fine."

He also rejected suggestions that the concept would not work outside London. "It doesn't really fit into a class or an eco paradigm," he insisted. "Where it works is local. About 70% of our 650 members are local. So long as there's a sense of identity and trust, it works."

Barrie said that someone had expressed serious interest on Twitter in setting up a version of the store in Glasgow. "We want people to copy us," he said.

He added that the store was now breaking even and had cost just £100 to fit out, having received donated shelving from a "supermarket giant".