A former cabinet minister has accused a barrister of deceiving a court to successfully block the prosecution of a headmaster who had been accused of sexually abusing five boys.

In a debate in the House of Commons on Wednesday, the Conservative MP Cheryl Gillan alleged that the QC, Andrew Bright, “gravely” misled the court while he was representing the headmaster.

Gillan alleged that the QC failed to disclose evidence to a judge who ruled that the headmaster, Peter Wright, would not be prosecuted for the offences.

The MP alleged that had this “hidden” evidence been disclosed, it would probably have undermined the attempt to have prosecution blocked.

A decade later, Wright was convicted in a related case of abusing five other boys while he was headmaster of Caldicott prep school in Buckinghamshire and jailed for eight years.

The allegation against Bright was made by Gillan in parliament, which means she is protected from being sued.

Bright now sits as a judge at St Albans. A spokesman for the judiciary said: “The Solicitors Regulation Authority conducted an independent investigation and rejected the complaint that the court had been misled. It maintained that conclusion after a review.”

Gillan, the MP for Chesham and Amersham, also alleged that a series of authorities – including the attorney general’s department, the crown prosecution service and legal regulators – did nothing to correct the failure to disclose the evidence.

The MP, who was secretary of state for Wales in David Cameron’s government, highlighted the case of Wright, who was the headmaster of Caldicott between 1968 and 1993.

He and three other members of staff have been convicted of sexually abusing boys at the fee-paying school in the 1960s and 1970s.

In 2003, prosecutors prepared to bring Wright to court on 16 charges of sexually abusing boys at the school between 1964 and 1970 while he was a teacher and then headmaster.

Before the case came to trial, lawyers for Wright, then 73, submitted an application to block the prosecution on the grounds that he would not get a fair trial as the allegations were three decades old. In legal terms, this is called a stay of indictment.

On Wednesday, Gillan alleged that Wright’s lawyers misled the judge at Aylesbury crown court, Roger Connor, by failing to disclose relevant information.

“The information could have meant that Connor could probably have considered the stay of indictment not at all justified,” she claimed.

She alleged that Wright’s lawyers had corresponded with the school about obtaining lists of former boys who could be called as witnesses for him. She alleged that his lawyers had “acted improperly” when they told the judge that these lists could not be obtained from the school.

“Had this correspondence been disclosed to the court, it could have assisted the prosecution in opposing the application for the stay and would, in all probability, have undermined the grounds of the application,” she said.

“However neither the judge nor prosecuting counsel ever saw this correspondence because it was never produced in open court, even though counsel for the defendant, AJ Bright QC, according to the transcript of the proceedings, had it with him in court, and thus was aware of its contents.”

Gillan added that the content of the “hidden correspondence” became known publicly five years later when it became apparent that the court “had been misled and in effect deceived into making the order” for the stay.

She said that the pupils’ concerns had grown after prosecutors had decided to prosecute Wright for sexually abusing five other boys and believed that he was going to argue that this second prosecution should also blocked on the same grounds.

Lucy Frazer, the solicitor general, told parliament that she was not aware of any findings of misconduct by lawyers in the case.