Michael Martin, the former Commons Speaker, became the latest senior figure to speak out against antisemitism in Labour on Sunday when he called for a special one-day conference to address the problem.

In a rare intervention in party politics for someone who had to quit the party whip when he became Speaker, Lord Martin said he was “appalled” by what was happening in Labour and that failure to tackle antisemitism could cost it the next election.

Stressing that he was not criticising Jeremy Corbyn personally for the problem, the former Labour MP, who now sits on the crossbenches in the Lords as Lord Martin of Springburn, said a special conference would allow party members to show how strongly they were opposed to antisemitism.

Martin’s intervention came as Labour confirmed that Corbyn has suspended his personal Facebook account. Party sources said it was administratively simpler for Corbyn to have just one Facebook account – he has retained his official one –although the move came as the party faced fresh criticism over senior officials belonging to Facebook groups where antisemitic messages were posted.

In an interview with the Guardian, Martin said that he had decided to speak out because ill health meant he could not attend the protest organised by Jewish leaders outside parliament last Monday, saying Labour should take antisemitism more seriously.

“You recall the saying, ‘evil happens when good men do nothing’. I have not been attending parliament because I’m on sick leave, but if I had been there on Monday last week, I would have joined the protest,” he said.

“I don’t want anyone ever coming back to me and saying, ‘Michael, you said nothing about antisemitism.’”

Martin said he believed antisemitism was a genuine problem within Labour and he rejected the argument that those raising concerns about it were only doing so to attack Corbyn.

“If you ran a restaurant, and it was dirty and there were cockroaches, you wouldn’t get away with saying ‘the restaurant down the road is dirty and has cockroaches too’. You would be expected to sort out the problem,” he said.

Martin said that, although the media were demanding answers from Corbyn, it would be better if ordinary party members could attend a one-day conference – a mechanism that has been used by Labour in the past to resolve specific disputes – to express their abhorrence for antisemitism.

“I think the time has come when we’ve got to get a one-day conference – that conference can be done in a regional basis, or in a national basis – but we need the membership to come together and say: ‘In no circumstances are we antisemitic. We are a democratic party and we thrive on decency,’” he said.

Martin, the first Catholic to serve as Commons Speaker since the Reformation, said there were personal reasons why he felt so strongly about this issue. His uncle was killed in the second world war, and his father served at sea, surviving a U-boat attack. He said he did not want not people to forget the sacrifices that were made by that generation in the fight against fascism and antisemitism.

He also said one of the people who most inspired him most to go into politics was Myer Galpern, the first Jewish Lord Provost of Glasgow and a subsequent deputy speaker of the House of Commons.

“The only way that the Labour party can improve the quality of life for men and women, and children, is if they are elected to public office and they have a parliamentary majority,” he said. “And if Labour is seen as antisemitic, then that is going to be at risk.”

On Sunday, the Sunday Times reported that a two-month investigation into 20 of the biggest pro-Corbyn Facebook groups had uncovered more than 2,000 racist, antisemitic, misogynist, violent and abusive messages. Twelve senior Labour staffers were members of these groups, it said.

The paper did not provide evidence of any of them posting or supporting offensive messages, and a Labour source said the staff members identified by the paper were adamant they had not seen the offensive material in question.

Labour insiders dismissed a report in the Times claiming that the party is facing a worrying fall in membership. The newspaper claimed that 3,000 members refused to renew direct debits last week, but a source familiar with the latest internal figures said this was not a figure that has been reported to the party.

The Times also said the party had lost 17,000 members since the start of the year, a drop off rate of about 3%. Membership was more than 570,000 after the election.

But the source said these were misleading figures that did not take account of people joining and that there was nothing unusual about the trend in recent months.

