Conservatives have attacked "seriously absurd" human rights legislation and called for a rebalancing of safety and liberty following last month's terrorist attacks on the US.

"We can not lecture others on the need for a global war against terrorism if we cannot take effective action at home," shadow home secretary Oliver Letwin told the Conservative conference.

"For our self-defence, we can not rely exclusively on action abroad. We must also consider our domestic security," he said.

At a gathering dominated by the international war against terrorism, the shadow home secretary told Tories that he supported the government's domestic efforts to make the UK a safer country.

But in his debut home affairs speech, Letwin launched a challenge to "seriously absurd" British human rights laws which prevent the government acting to protect its citizens.

"The situation in which we find ourselves is absurd - seriously absurd," he said. "The cause of this absurdity is a tangle of laws, conventions and jurisprudence."

Letwin attacked the Human Rights Act for stopping home secretary David Blunkett removing suspected terrorists from Britain, or preventing their entry in the first place.

"At the centre of this web lies the European convention for the protection of human rights which has become part of our law through the government's Human Rights Act," he said.

Conventions protecting the rights of refugees - including article three of the Human Rights Act - block deportation if there is a risk of torture or execution.

And such measures came under heavy fire from Tories meeting in Blackpool under the slogan of "Security abroad, security at home". Letwin called for changes to the HRA - which Tories argue could even lead to court challenges over extradition of UK suspects of the New York attacks to the US because they could face execution there.

"Protecting our own security is not just a question of enforcing the law. It is also a question of having the right laws," he said.

"We will not listen to the voices of those whose minds have failed to engage with the seriousness of the threat or with the inadequacy of our current protection against it."

The move follows Blunkett's frustrations at human rights court rulings on immigration and may allow the Conservatives to outflank the home secretary in imminent Commons debates on emergency legislation to crack down on terrorists.

Letwin's tough approach was, however, tempered with calls to carefully target actions at suspects and opposition to any emergency legislation that infringes on the civil liberties of UK citizens.

"The action we take must be targeted; in seeking, rightly, to protect our free society, we must jeopardise the very liberty, which makes that society so precious to us," he said.