Liberal Democrat peer Lord Lester of Herne Hill is also arguing that serving law lords should no longer take part in parliamentary debates.

Constitutional Affairs correspondent Joshua Rozenberg outlines the debate

As well as being a senior cabinet minister and speaker of the House of Lords, the Lord Chancellor is also head of the English judiciary - Lord Irvine has sat twice as a judge since taking office in 1997.

Unlikely to agree

In the House of Lords on Wednesday, Lord Lester will argue that the Lord Chancellor should no longer sit as a judge. Lord Lester thinks it may turn out to be against the new Human Rights Act for him to do so.

Lord Irvine is unlikely to agree - successive Lord Chancellors have said that having a foot in both camps helps them liaise between judges and politicians.

Lord Lester will also propose that the law lords should no longer take part in House of Lords debates. The government says that the law lords do not become involved in politically controversial issues, but Lord Lester believes this no longer holds true.