Analysis By Nick Assinder Political correspondent, BBC News website

David Cameron believes he has finally found something to help him defeat Tony Blair over law and order.

Cameron wants Bill of Rights

By pledging to scrap the Human Rights Act, he has zeroed in on an issue that has become, in many minds, a symbol of where Labour has got it wrong, particularly on terror suspects.

There is a growing belief - rightly or wrongly - that since the European Convention on Human Rights was written into British law six years ago the criminal justice system has been thrown out of balance.

It is often claimed that the effect of the act has been to see the rights of offenders routinely given precedence over the rights of victims.

Tony Blair has helped put the issue top of the law and order agenda by delivering keynote speeches about the need to rebalance the criminal justice system.

And there seems to be cross-party agreement that the act is not working properly.

Fundamental rights

But the prime minister has attracted criticism for suggesting it is judges' interpretation of the law, rather than the Act itself, that is at fault. There is currently a government review underway but it is unclear whether amending the law is on the cards.

The Act is widely supported by the Labour Party and he seems set to keep it.

Blair put human rights issue on agenda

So David Cameron has spotted a gap in the market and moved to fill it with his proposal, which would replace the act with a Bill of Rights.

He argues that would not only rebalance the criminal justice system but codify some fundamental British rights.

The European Court of Human Rights would then have to consider those British rights when ruling on cases brought before it - something that would still happen as Mr Cameron has no plan to withdraw from the European convention.

The policy throws up numerous questions about how the Bill of Rights will be drawn up, what will be included and whether it amounts to the start of a written constitution - questions Mr Cameron admits he cannot yet answer.

Voting soft

Critics claim it is the wrong way forward because the convention would still apply and that, in any case, it is law and order policy, not the Act, which is the problem.

And they are warning against dismantling fundamental human right's laws.

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But, for the time being at least, Mr Cameron has probably scored a hit - with headlines declaring he is set to scrap the Human Rights Act certain to strike a chord with voters.

While Tony Blair is accusing him of "talking tough but voting soft" on law and order, Mr Cameron is declaring that, under his leadership, the Conservative Party is "determined to provide a hard-nosed defence of security and freedom".

It is that core, tough message that he undoubtedly hopes will filter through to the public and which is likely to be the nub of attacks he will continue to launch on Tony Blair over the criminal justice system.

Nick.Assinder-INTERNET@bbc.co.uk