Clifford Chance (CC) has been instructed to advise a group of judges fighting upcoming changes to their judicial pensions proposed as part of the Pensions Bill 2011.

The magic circle firm has been asked to obtain quotes for legal advice for the action group from leading counsel.

The move comes in response to the the Pensions Bill 2011, which started its progress through Parliament earlier this month and which will mean judges will have to contribute to their own personal pensions for the first time.

Under the current scheme, judges contribute 1.8% of their salary towards their spouse's pension, with their own pensions wholly-funded by the state.

The proposed changes, which follow publication of Lord Hutton's report on public service pensions published in March last year, would see the judges also have to contribute 1.28% of their salary to fund their own pension from April this year.

A report in The Times last week suggested that the judges are arguing that their constitutional independence makes them a special case, and that ministers would be acting unlawfully were they to proceed with the changes.

In a statement the Judicial Office said: "Confidential talks between the Lord Chancellor and Lord Chief Justice are continuing on pension reform."

A Ministry of Justice spokesperson said: "Lord Hutton's interim report concluded there is a clear rationale for public servants to contribute more towards their pension costs so they remain fair to taxpayers and employees, and affordable for the country – this includes judicial pension schemes.

"In April the Government will implement progressive changes to member contributions, leading to savings of £2.8 billion a year by 2014-15. From April personal judicial contributions of 1.28% will be taken from judges who have not accrued full pension benefits as part of these savings."

According to The Times, between 350 and 400 judges are gearing up to contest the pension reforms at all but the most senior levels.

Judicial salaries range from £95,000 for judges at first-tier tribunals through to £240,000 for the Lord Chief Justice.