HRA or Bill of Rights
1. It's xenophobic. The 'political' argument as purported by the Labour Party, Lib Dems and Ken Clarke, as well as the traditional Guardianista bunch. I don't think this washes to be honest. One of the problems with the HRA is that it is a straight import of a law written (albeit partly by English lawyers) with the European code of law in mind. Thus problems with incompatability are dealt with by judges, not politicians. In Europe this is not controverisal, as the majority have written constitutions which are interpreted by constitutional courts anyway. In Britain this is a fundamental alteration of our constitution and has caused problems for that reason. A rewrite of the Act designed to ameliorate this situation is clearly not xenophobic, any more than redesigning a French car to right-hand drive would be.
2. It's unenforceable. The 'constitutional' argument, as stated by, among others, Tim, the DK and Nosemonkey. This states that since it is impossible to entrench legislation in Parliament, any statute passed would be, effectively, good only for as long as the Government that passed it. This is of course entirely correct. It is also rather irrelevant. No, you can't entrench legislation in the British constitution. This applies as much to the HRA as to any prospective Bill of Rights. Tim Worstall says that you could sign an international treaty to circumvent this problem, but there's already precedent (Mortensen v someone or other if you want to know) to say that any British statute, however minor, trumps any international treaty, however, major. With the HRA, the power of the judges is embarrassment, no more and no less. If a statute passed by Parliament is in contravention of the HRA the judges can say that, but no more. If a British citizen takes a case to the ECHR, all they can do is make a 'precatory' judgment - they have no power to enforce it in this country.
3. It's unnecessary. The 'practical' argument also espoused by Labour and the Lib Dems. This states that, since any new Act would be based on the fundamental human rights espoused in the EDHR it would only be a re-statement of the HRA and thus irrelevant. I don't agree with this either. The law in its current form states rights, such as 'to privacy' and their qualifications, such as 'in the public interest'. It is then the job of the judges to determine if an action of the Government is in conflict. A better system would be one where the rights and qualifications were set out, and the job of balancing these was left to the minister responsible. The judges could then adjudicate on the existing basis of judicial review. To those who would argue that allowing ministers to determine what balance would be struck would emasculate the act, there is an answer. This is a democratic society, built on a 'living constitution'. Accordingly, we are governed by those we elect, and by no other force. We do not have a written constitution to provide a framework, nor yet any way of creating one.
The Human Rights Act is deeply flawed, not in concept but in execution. It takes a continental legal concept, and superimposes it on a Common law system. What Cameron is proposing might be a remedy to this. It might of course be nothing more than a cheap stunt, but the possibility remains that it is instead a workable solution to an identifiable problem.