David Cameron has promised one of the biggest constitutional shake-ups of recent years, calling for a new "bill of rights and responsibilities" to replace the contentious Human Rights Act.
In what would amount to a leap towards a written constitution, the Conservative leader will today call for the adoption of the equivalent of Germany's "basic law", a domestic constitutional doctrine that would give the courts more leeway when interpreting European human rights conventions.
Mr Cameron will say a bill of rights would enshrine ancient traditions, such as the right to trial by jury, and provide greater "clarity and precision" on fundamental rights, making it "harder to extend them inappropriately as under the present law".
By seizing the initiative, Mr Cameron is capitalising on the government's ambivalence towards its own Human Rights Act, which was introduced in 1998.
He is also staking a claim to territory that some of the allies of Gordon Brown say the chancellor would try to occupy as a sign of renewal of the government's agenda.
The act incorporates European human rights rules into domestic law. But faced with a series of uncomfortable and unpopular court rulings on human rights grounds and the inability to deport foreign terror suspects, Tony Blair suggested the act should be amended.
He has since backtracked but still insists interpretation should be rebalanced to protect national security.
Mr Cameron will argue that a bill of rights would solve the problem because the European courts would then give Britain the same "margin of appreciation" that they afford other countries.
In a speech to the Centre for Policy Studies, Mr Cameron will attack the Human Rights Act for "introducing a culture that has inhibited law enforcement" and for thwarting the deportation of foreign terror suspects who pose a threat to national security. But he will defy the instincts of some rightwing Conservatives by ruling out either scrapping the act or withdrawing altogether from the European Convention on Human Rights.
The former, he will say, would mark a "step backwards on rights and liberties" and simply force people to take the longer and more costly route of appealing to the European Court of Human Rights in Strasbourg. The latter would leave citizens dependent on ancient rights which in Britain's common law system cannot be protected from an overweening executive.
To give a bill of rights more permanence under Britain's common law system, Mr Cameron will suggest it would not be possible for parliament to change it without the consent of the House of Lords, a move that would prevent a future government amending it using the Parliament Act.
Lord Goldsmith, the attorney- general, attacked Mr Cameron's proposals as "muddled, misconceived and even dangerous" because they risked creating competing sets of rights for the UK courts to grapple with.