Two judges at the centre of a blackmail trial involving their former cleaner will face a formal investigation.

The Lord Chancellor and Lord Chief Justice took the decision after it emerged that both judges employed Brazilian Roselane Driza illegally.

They have decided there were "sufficient grounds" to ask the Office for Judicial Complaints to conduct a preliminary investigation.

The inquiry will establish whether there is any case for them "to exercise their disciplinary powers", the Department for Constitutional Affairs said.

Mohammed Ilyas Khan, 60, and his former lover, a fellow immigration judge known only as J, have been asked not to sit while the investigation takes place. Driza (37) faces up to 14 years jail and deportation after she was convicted at the Old Bailey last week of blackmailing J and stealing two sex videos from Judge Khan, who became her lover.

But she was cleared of blackmailing Judge Khan, with whom she was living up until her arrest.

In a ground-breaking ruling, the Recorder of London, Judge Peter Beaumont, lifted an order that had banned Judge Khan from being named.

Kenyan-born Judge Khan had previously worked at St Philip's Chambers in Birmingham and his ex-wife still lives in the city. He was made a recorder in 1996 and promoted to an immigration judge last year.

In a statement yesterday the DCA said: "The Lord Chancellor and the Lord Chief Justice strongly believe that the public must have confidence in judges and take seriously any allegations against them of misconduct.

"The Lord Chancellor and the Lord Chief Justice have considered carefully the issues that have arisen about the conduct of the two immigration judges, one of whom also sits as a Recorder, following the trial of Miss Roselane Driza.

"They have concluded that there are sufficient grounds to ask the Office for Judicial Complaints to carry out a preliminary investigation."

Judge Khan will remain on full pay while J, who has been off work due to stress for the last 18 months, will continue her previous sickness pay arrangements.