The prime minister is undermining public confidence in the rule of law and the judiciary

The writing was on the wall when Tony Blair sacked Charles Clarke and installed John Reid as home secretary. Clarke had resisted ill-conceived and illiberal law-and-order gimmicks invented in Downing Street to appease the rightwing press. In the wake of the disastrous local elections, however, the prime minister decided to pick a populist fight against the judges and liberal politicians. He commanded a more compliant home secretary to "look again at whether primary legislation is needed to address the issue of court rulings that overrule the government in a way that is inconsistent with other EU countries' interpretation of the European convention on human rights".

The lord chancellor, Derry Irvine, would surely have explained that it is the function of the European court of human rights, in partnership with national courts, to interpret the European convention , not "other EU countries". He would have reminded the prime minister that each of the 46 member countries of the Council of Europe has made convention rights part of its constitutional and ordinary laws. He would have commended British judges for giving effect to the Human Rights Act by striking a balance between individual rights and the wider public interest. He would have added that British jurisprudence now strongly influences the Strasbourg court.

He might have suggested that it would be useful for Mr Blair to make a major speech explaining how the Human Rights Act protects the civil and political rights of everyone, not only minorities: the right to life, and freedom from torture or other ill-treatment; to liberty without arbitrary arrest or detention; to freedom of speech, assembly and association; to fair trials by independent and impartial courts respecting the presumption of innocence; to personal privacy; to a home and private property; to education; and to equal treatment without unfair discrimination.

The prime minister could explain how the convention enshrines British values and shields the governed against abuses of power by their governors. He could recall how the British drafters of the convention made sure that public safety was at its heart, qualifying individual rights with the needs of national security, the prevention of disorder or crime, and the rights and freedoms of others.

But this is fantasy. Mr Blair has never warmed to the Human Rights Act - a project inherited from John Smith and carried through by Lord Irvine and Jack Straw with Liberal Democrat support, in the teeth of opposition from the Conservatives and the rightwing press. The lord chancellor resisted an attempt by the tabloid lobby to immunise itself from the risk that the Human Rights Act would encourage a right of personal privacy. The attack on the act and the convention, now led by the Sun and Cameron's new Conservatives, is driven by commercially motivated self-interest.

Instead of resisting these pressures, the prime minister has caved in again and again. In 2003, on the BBC's Breakfast with Frost, he said that the position regarding asylum and illegal immigration was "unacceptable" and that ministers would "fundamentally" re-examine the UK's obligations under the convention. After the London bombings, he again threatened to weaken the Human Rights Act, to make it easier to remove suspected terrorists and accomplices. The prime minister said: "Let no one be in any doubt, the rules of the game are changing." By this he seemed to mean that the convention and the Human Rights Act needed changing.

As well as instructing his new home secretary last week, Mr Blair decided to take another swipe at the judges. When Mr Justice Sullivan held that there had been an abuse of power at the highest level of government in seeking to flout a judicial decision on the right to asylum of the Afghan hijackers, the prime minister disparaged the judgment as "an abuse of common sense". He knew that the judge could not reply. He chose to attack a judgment without reading the judge's reasons and before the Home Office had decided whether to appeal.

The Human Rights Act was New Labour's first constitutional reform. Yet Mr Blair persists in undermining public confidence in the rule of law and the protection of human rights by the senior British judiciary. Instead of defending the act and the judiciary, he joins the chorus of critics. Having sown the wind of ignorant opposition, he and his government reap the whirlwind.

It is a misfortune that there is no one in his cabinet able to adapt Attlee's advice to Harold Laski: "A period of silence on your part would be welcome."

? Lord Lester QC is a human rights lawyer and Liberal Democrat peer