Senior judicial officials have been accused of attempting to cover up the findings of a top level inquiry into comments by Cherie Blair as she spared a violent criminal jail.

The National Secular Society (NSS) made a formal complaint after the wife of former prime minister Tony Blair told a devout Muslim he would not go to prison because he was a "religious person".

The comments, which were made by Mrs Blair as she sat as a part-time judge at Inner London Crown Court, were considered by the Lord Chancellor, Kenneth Clarke, and the Lord Chief Justice, Lord Judge.

A statement released by the Office of Judicial Complaints (OJC) said her actions "did not constitute judicial misconduct" and "no disciplinary action is necessary", suggesting Mrs Blair had been cleared.

But a letter sent directly to the NSS marked "restricted - personal" said Lord Judge and Mr Clarke ruled the complaint was partly upheld and "expressed some concern" about the impact of her comments.

It also said Mrs Blair would receive "informal advice" from a more senior judge about her comments, although it claimed this was not a "formal disciplinary sanction".

Keith Porteous Wood, who leads the NSS, accused the watchdog of a "cover-up", making a "partial and misleading statement" and of trying to "silence" his organisation with an intimidating letter.

He said: "Advice we received throws doubt on the OJC's right to seek to make its adjudications on our complaint confidential, especially in a case where it itself has put such an incomplete account of its findings into the public domain.

"It is worrying that a decision made by the Lord Chancellor and the Lord Chief Justice should be so deliberately concealed in this way. What happened to justice being seen to be done?"

Questions were raised after Mrs Blair, who sits as Cherie Booth QC, told Shamso Miah he would not go to prison after breaking a man's jaw during a row over queue-jumping in a bank "based on the fact you are a religious person".