The case, marking a low point in relations between the Government and the judiciary, will see the group accuse Ms Truss of unlawfully discriminating against them on grounds of their age. 

In addition, the six will also claim that Ms Truss — who has only held the dual role of Lord Chancellor since July — discriminated against them on the grounds of ethnicity and sex in the case, which relates to a new judicial pension scheme. 

According to legal affairs journalist Joshua Rozenberg QC on Facebook, the claims relate “to reduced benefits the judges can expect to receive under a new judicial pension scheme introduced last year”. 

While some judges were allowed to stick with the old scheme, others – including the six bringing the legal action – were automatically enrolled onto the new pension arrangement, because they were under a certain age.  

A two-week hearing has been arranged before a tribunal judge who is not affected by the new pension arrangements. There could be further hearings before appeal judges. 

The six High Court judges bringing the action are Sir Nicholas Mostyn, 59, Sir Roderick Newton, 58, Sir Philip Moor, 57, Dame Lucy Theis, 55, Sir Richard Arnold, 55 and Sir Rabinder Singh, 52. 

The news comes after Ms Truss came under heavy criticism for her response to the press abuse faced by three High Court judges who ruled that Parliament must be given a vote before Britain triggers Article 50, launching the Brexit process. Chantal-Aimée Doerries QC, the chairman of the Bar, the representative body for barristers in England and Wales, said the Cabinet minister had a duty to uphold the rule of law.  

“Her job is sometimes called the conscience of the government and one would expect her to speak out on something like this,” she said. 

Under huge pressure to defend the independence of Britain’s judges, Ms Truss issued a terse statement on Saturday (November 5), observing: “The independence of the judiciary is the foundation upon which our rule of law is built and our judiciary is rightly respected the world over for its independence and impartiality.” 

Lord Falconer QC – a former Lord Chancellor himself – called for Ms Truss to be replaced. 

Penning a letter for The Times, Lord Falconer claimed that the judiciary had lost its “constitutional protector”, and that the Justice Secretary should “be replaced by someone willing and brave enough to do the job”. 

Until this happens, says his Lordship, “the judges should rightly fear for their independence”.