A judge has ruled that criminal proceedings relating to a former Labour peer accused of child sex abuse should be halted, saying the way evidence was disclosed to his defence team was “disgraceful” and had “sabotaged” his trial.

Nazir Ahmed who was Lord Ahmed of Rotherham before he resigned from the House of Lords last year, went on trial in Sheffield last month accused of sexually abusing a younger boy and girl when he was a teenager in the early 1970s.

The trial was halted by Judge Jeremy Richardson QC two weeks ago.

On Monday, he took the unusual step of ordering a permanent stay on proceedings, bringing the prosecution to a halt, but a restriction prevented this from being reported until a further hearing.

On Tuesday, Tom Little QC, prosecuting, confirmed the Crown Prosecution Service (CPS) will appeal against this decision and Judge Richardson’s order will not take force until the appeal is heard.

But the judge ordered that all reporting restrictions relating to the case will be lifted so details of his ruling could be published.

Judge Richardson said he was “shocked and appalled” that information was being supplied to the defence even during the trial, despite the allegations dating back nearly 50 years, the trial being postponed for a year due to Covid and the allegations being first made almost five years ago.

He said: “This disgraceful situation has sabotaged this trial and caused it to abort. I do not use this adjective lightly.”

Ahmed resigned from the upper chamber after a Lords conduct committee report recommending the first expulsion of a peer was approved by the House of Lords.

The report found he had breached the code of conduct “by failing to act on his personal honour”.

Ahmed, 63, went on trial at Sheffield Crown Court last month after denying two counts of attempting to rape a girl under 16, indecent assault of a boy under 14 and raping a boy under 16, all said to have occurred in the early 1970s.

His brothers Mohammed Farouq, 70 and Mohammed Tariq, 65, also from Rotherham, were accused of indecent assault of a boy under 14, but were deemed unfit to plead and faced a trial of the facts during the same proceedings.

Judge Richardson said he was “extremely concerned” about apparent failures by the police to follow up reasonable lines of inquiry, saying the case had been handled “as if we’re in a different era”.

The judge admitted he had always “harboured grave misgiving about the wisdom” of the prosecution due to the antiquity of the allegations and vagueness of what was alleged.

But he said this was not the reason he took the decision to stay the proceedings, a ruling he said he had never made before.

Judge Richardson said that despite the prosecution’s “massive and fundamental failure” to stick to disclosure rules, it was normal to let them “put it right and have another go”.

But he said he had decided to take this unusual course of action in the light of a number of other factors, including what he saw as the weakness of the prosecution case.

He said the “calamity” had gone from “bad to worse” and he had come to the conclusion that “enough was enough”.

Judge Richardson said he understood this outcome was “unsatisfactory for everyone”.

He made it clear this was not a “not guilty” verdict for the defendants and he also said the complainants “may feel cheated”.

But he said the actions of the prosecution had “blown this case apart”, and he had to put a stop to the “the agony of it continuing”.

Judge Richardson repeatedly indicated his concerns about the case throughout its progress through the system.

At a hearing last year, he stressed the antiquity of the allegations noting that some of the alleged incidents happened in the late 1960s when Harold Wilson was prime minister, Lyndon Johnson was the US president and the Vietnam War was raging.

“I’m testing my own recollection to the full, but it was during 1968 that Martin Luther King was assassinated and, indeed, Robert Kennedy too was assassinated,” Judge Richardson added.

And he went on: “It was in 1971 that the UK adopted decimal currency and the Watergate scandal was yet to happen – again revealing how long ago this was.”

A CPS spokesman said: “We are appealing this decision and have explained this to the two complainants. If our appeal is successful we will seek another trial of the defendants.

“In the meantime we will consider the judgment and ensure that lessons are learned from the issues in this case. We will continue our work to drive lasting improvements in our handling of disclosure to ensure that we provide the service the public rightly expect.

“The issues surrounding this case do not change our commitment to prosecuting non-recent allegations of sexual abuse where our legal test is met.”