Tony Blair and his Lord Chancellor, Derry Irvine, will be plunged into a fresh row over cronyism this month as damning new evidence emerges of how government jobs are handed out.

An industrial tribunal is investigating how a barrister from Irvine's former chambers - where Tony Blair and Cherie Booth used to work - was given a lucrative government role.

Last month Irvine was found guilty of sexual discrimination when he appointed long-time friend Garry Hart as a special adviser. Now Labour will come under attack over how it appointed Philip Sales to the coveted post of Treasury 'Devil' - one of the Government's chief barristers, who acts for the state in the civil courts.

The 1997 appointment of the 35-year-old barrister caused astonishment among senior lawyers because he was 'exceptionally young' for a high-profile job regarded as a near-certain route to becoming a High Court judge.

Sales had been on the panel of government lawyers for only a few months, and had much less experience in public law than three front-runners who were passed over.

The appointment means the old chambers of Irvine and Blair have profited more than any other legal chambers from doing work for the Government - 11 King's Bench Walk in London's Middle Temple has been paid more than pounds 36,000 of taxpayers' money since Labour came to power in May 1997. The figure is five times the average paid to the 24 chambers who have carried out legal work for Irvine's department.

A woman barrister, Josephine Hayes, claims the Government was guilty of sex discrimination in the way it appointed Sales. The case will be heard at Croydon industrial tribunal on 21 June.

Despite fierce opposition from senior judges, Hayes's lawyers have been able to obtain details of the 'secret soundings' taken before his appointment.

According to sources close to the case, the details reveal a 'network of old boys and cronies' and show that 'there was no coincidence that the appointment came from Lord Irvine's and Tony Blair's old chambers'.

As well as being another significant blow for the Lord Chancellor, the case is threatening to expose the shadowy system of 'secret soundings' used to select QCs and judges.

This is done entirely by word of mouth, and in Sales's case was conducted by Lord Falconer, Solicitor-General and a close friend of Blair. Senior judges opposed the disclosure of their comments, claiming it was in the public interest to keep them secret.

Irvine had a key say, and others consulted included Lord Bingham, the Lord Chief Justice, Lord Woolf, Master of the Rolls, and Sir David Keene, a close friend of the Blairs in whose French holiday home they often stay.

Michael Supperstone, chairman of the administrative law bar association, and also a member of Lord Irvine's former chambers, was also consulted.

Irvine's political career continues to be dogged by controversies. Aside from the recent tribunal verdict that found him guilty of indirect sexual discrimination, he was attacked for spending over £300 a roll on wallpaper for the residential apartment in the Palace of Westminster.

Irvine set up 11 King's Bench Walk in 1981. Blair practised there until 1984, a year after he became an MP, and it was there he met Cherie.