Mr Lammy has repeatedly claimed that 60 per cent of rape victims withdraw from cases because of court delays.

In reality, the vast majority of rape complaints fall away long before any charge is brought, often due to investigative delays, with only eight per cent of them withdrawing after a charge has been made.

In an interview with Sky News, he said: “If a woman is, sadly, raped in our country today, she will likely have her trial come on in 2028, maybe 2029. That’s a long time for her to wait.

“Victims of rape are pulling out — 60 per cent are pulling out of cases — witnesses fall away, and the trauma of waiting is too hard.”

That figure was also circulated to Labour members in a 13-page briefing urging MPs to defend the proposed reforms with the phrases they should use, including: “In rape cases, 60 per cent of those who report being raped are now pulling out before trial.”

Andrew Thomas KC, of the Criminal Bar Association, said delays undoubtedly inflict serious harm on complainants — especially in sexual offence cases — but warned that the debate must be grounded in evidence.

“That includes using relevant statistics in a proper fashion,” he said.

“Justice, as the secretary of state for justice should know, begins only when there is a charge to bring a criminal case to court — all forms of rape included.

“The only accurate measure from a court perspective is the CPS [Crown Prosecution Service] measure of how many of its prosecutions fall away due to witness attrition and that remains, on average for the past year, around eight per cent.

“To include figures relating to allegations brought to police does not assist in this debate and may lead to erroneous conclusions.”

The Ministry of Justice dismissed the criticism as “completely misleading”, insisting that Mr Lammy “has been clear that justice delayed is justice denied” and arguing that long waits deter victims “at all stages”.

Baroness Kennedy, a Labour peer and human rights barrister, said: “This has all the appearances of a policy that’s been put together on the back of an envelope by talking to lawyers who’ve never done a jury trial in their life.”

The Ministry of Justice stated: “Our crucial reforms will put victims first, creating a fairer system that offers vital support to victims of rape and sexual violence, cuts the court backlog and gives brave survivors of crime the swifter justice they deserve.”