Karl Turner, the former shadow solicitor general and MP for Kingston upon Hull East, said he was “ashamed” of both the prime minister and the justice secretary, David Lammy, and urged them to “stop these ludicrous proposals and get on with the hard job of sorting out the criminal justice system”.

Under the government’s proposals, juries would be removed from trials where the likely prison sentence is three years or less, while routes of appeal from magistrates’ courts to the Crown Court would be restricted. Legislation has not yet been introduced.

Mr Turner last week became the only Labour MP to break the whip and vote against the plans, backing a Conservative motion. He said he was unconcerned about disciplinary action and had warned party whips he would consider resigning to trigger a by-election to make a “principled point”.

In an interview with The Sunday Times, Mr Turner disclosed that he had been charged with handling stolen goods in 2002 while working as an antiques dealer in Hull. The case collapsed before trial, but he said the experience convinced him that, as a working-class man, he would have been treated more fairly by a jury than by a judge. He believes juries act as a safeguard against prejudice.

Mr Turner said the episode shaped his decision to pursue a legal career and ultimately enter politics. He added that his opposition had struck a chord within the party, with around 40 Labour MPs signing a letter calling the proposals an ineffective response to court backlogs.

Ministers argue that judge-only trials would be around 20 per cent quicker and help reduce delays for victims and witnesses. Mr Lammy is currently examining similar reforms in Canada. However, critics including senior lawyers, academics and civil liberties groups say the changes risk undermining protections against miscarriages of justice.

Mr Turner said: “Keir keeps saying that he’s anti-ideological. He loathes the idea of ideology in politics apparently. He is a pragmatist. So why does he allow his courts minister to ’fess up to the fact that this plan to do away with the right to elect for jury trial in serious criminal cases is ‘ideological’ and in fact she would be doing it even if there was no backlog in the crown courts?

“So why are we doing this? The only possible reason is that Lammy has offered up savings to the Treasury. I’ve asked the chancellor what the savings are and she has suggested to me that the exchequer secretary will be asked to speak with me but I also intend to table parliamentary questions on what the savings are. I am convinced that any savings will be outweighed by the need to recruit judges, train judges and administer these new so-called [Crown Court Criminal Division] single judge courts.”

Although Mr Turner holds a majority of just under 4,000, he said he believed the government would ultimately be forced to retreat in the face of growing opposition within its own ranks.