Campaigners calling for a referendum on the voting system in the wake of the expenses scandal took their protest to Ann Keen’s constituency office.

The demonstrators, from Vote for a Change, targeted the Brentford and Isleworth MP’s office in Chiswick High Street on Tuesday, holding banners and posing as politicians sipping champagne on the Westminster Express.

Campaigner Willie Sullivan said: “This summer the Westminster gravy train hit the buffers. But we can’t let this opportunity to build a better politics be lost by its current passengers unwillingness to let voters make that change.

“MPs like Tony McNulty, Ann Keen and Claire Ward have to decide are they with the voters or against them?

“We’re not out simply to berate the villains of the expenses crisis. We’re out to expose the roadblocks to reform, those MPs who feel that voters don’t deserve the final say on the future of their parliament.”

Tom Beaton, of Church Street, Isleworth, said he joined the protest because he was concerned about the need for electoral reform.

The Green Party member said: “The big parties have started to realise they have to play the system, which means to enable them to get a majority in parliament they have to target a very small number of swing voters.

“The knock on of that is it corrupts the whole system, because Labour no longer cares about the voters it used to with the sort of principles it used to, and neither do the Conservatives appeal to the voters they used to, they are all grabbing the middle ground voters.

“One of the consequences is that, if MPs are not treating their constituents with contempt they are certainly behaving as if they are, and Ann Keen epitomises this.”

Mrs Keen was unavailable for comment but Steve Curran, chairman of the Brentford and Isleworth Constituency Labour Party, branded the protesters’ actions “irresponsible”.

“The actions of the vote for change group did not help the debate with regard to the reforms of the House of Commons,” he said.

“Their actions at the Labour Party Headquarters in Chiswick were irresponsible and caused considerable upset and distress to our business and residential tenants which led to valuable police resources being wasted by a group hell-bent on publicity at any cost.”

The group is to tour the country.