The former leader of Friends of National Museums Liverpool (FNML) has slammed NML, calling it "hypocritical" for adopting David Cameron's 'Big Society' volunteer plans.

The Prime Minister praised NML's volunteer scheme, where members of the public help keep the museums open for longer, in his Big Society proposal.

However, Andrew Pearce, former chair of the FNML, told the BBC it would be hypocritical for the NML board of trustees to "call out for volunteers when they previously had so many of them willing to give up their own time to help the museums".

The FNML was disbanded in April 2008 after an ongoing disagreement between the two entities about the way the museums were being run, specifically the International Slavery Museum. It ended with the FNML, which had a 1,700-strong membership, being kicked out of its Albert Dock headquarters and members having their privileges withdrawn.

Pearce said: "How dare NML now call for volunteers when it treated the volunteers it previously had in such a shabby manner? Would it treat new volunteers any better than it treated the previous Friends?"

Conversely, NML chair Phil Redmond countered, saying: "We want volunteers who are more hands-on on a daily basis, who will come in and help run the museums after five o'clock. At the moment our museums open for about seven hours a day - why shouldn't we extend this with the use of volunteers and have them open the museums at weekends?

"We train them up on health and safety and various other essential skills and they can help make a difference. It is not about replacing our staff - who I should not need to reassure because without them NML would not be where it is today. We just want make best use of the funding we receive from the government. And if they try and cut what we receive then I will be the first one fighting that."

Photograph: Before it disbanded, the FNML was particularly concerned about the way the International Slavery Museum was being run