The Conservatives' plan to replace the Human Rights Act with a US-style Bill of Rights has been described as muddled and dangerous by the government.
Mr Cameron accepts it would be difficult to draft the text
Tory leader David Cameron says current legislation is inadequate and hinders the fight against crime and terrorism.
He believes a British Bill of Rights would strike a better balance between rights and responsibilities.
But the Lord Chancellor says Mr Cameron is trying to rewrite human rights because "they seem inconvenient".
In a speech to the Centre for Policy Studies in London, the Tory leader argued that the Human Rights Act had prevented Britain deporting suspected terrorists whatever the circumstances.
It was "practically an invitation for terrorists and would-be terrorists to come to Britain" he said.
They knew that whatever crime they had committed or if there was a suspicion they might be planning a terrorist attack in the UK or elsewhere, they would not be sent back to their country of origin "because the process is so complicated and time-consuming for the government".
"I believe it is wrong to undermine public safety, and indeed public confidence in the concept of human rights, by allowing highly dangerous criminals and terrorists to trump the rights of the people of Britain to live in security and peace," he said.
Mr Cameron said a "home grown" document would be based on British traditions, balancing rights with security.
People would still be able to pursue their claims in the European courts but judges would have a British Bill of Rights to base their rulings upon, he said.
He stressed he did not want to withdraw from the European convention and acknowledged it would be hugely complicated to draft a Bill of Rights.
He is appointing a panel of distinguished lawyers to unravel those challenges for him.
But Lord Falconer, the lord chancellor, dubbed Mr Cameron's plans as unworkable and "a recipe for confusion, not clarity".
"It is utter nonsense to say that you solve the problems about crime and terrorism by introducing an additional layer of rights undefined," he told BBC Radio 4's PM programme.
"David Cameron made absolutely clear he's sticking with the convention. That means he's going to comply with the convention."
Attorney General Lord Goldsmith said the Tory proposal was "muddled, misconceived and dangerous".
"I think it would lead to more, not less, confusion about the best way to strike the balance between protecting the public and individual liberties," he said.
And Human rights lawyer Michael Mansfield QC described the plan as "complete nonsense".
"How is it hindering the investigation and prosecution of crime? No examples whatsoever. It certainly isn't doing that in relation to terrorism or terrorist cases," he said.
"I'm afraid it's totally misconceived and it's tabloid driven."
Lib Dem peer Lord Carlile, the government's independent adviser on terrorist legislation, said he could not see any benefit coming from "these extraordinarily ill-thought out proposals".
The Liberal Democrats have long campaigned for a British Bill of Rights and a written British constitution.
But Lib Dem leader Sir Menzies Campbell told BBC Radio 4's World at One that the suggestion that the European convention had "stood in the way of dealing with terrorism is frankly unfounded".
Ex-Conservative chairman Lord Tebbit warned that any British Bill of Rights could be overridden in Strasbourg as long as the UK remains signed up to the European convention.
The Human Rights Act has come under repeated attack in recent years from critics who say it puts a "rights culture" ahead of a common sense view of cases.
The act came into force in 2000 to install the European Convention on Human Rights into British law so people did not have to take claims to the European courts in Strasbourg.
A US-style Bill of Rights would outline the rights of citizens, while the Human Rights Act incorporates European rules into British law.