The prime minister has said that identity cards are vital for tackling fraud and immigration abuses.

Speaking at his monthly press conference in Downing Street on Monday, Tony Blair took on critics by claiming that a secure identity system would actually boost people's liberty.

Blair told reporters that the cards would bring four major benefits: security and managing migration; protecting vulnerable people; aiding criminal detection; and combating identity fraud.

He said this would bring tangible benefits such as making it easier to open a bank account, get a mortgage or driving licence and travel around Europe.

And he also argued that critics of the cost of the project were scaremongering by not taking into account the need to introduce biometric passports anyway and the cost of not taking action.

Earlier briefings suggested that ID cards could save £1.7bn by protecting against fraud.

And insisting he had widespread public support for the plans, Blair directly dismissed critics' complaints.

"People say this a large scale IT project, the government can't deliver such projects," he noted.

But he pointed to the successful delivery of new Department for Work and Pensions payments schemes and a new passport system.

"Then there are those who say identity cards are simply trading too much of our liberty," Blair added.

"Unsurprisingly the public don't have a problem with being protected by using CCTV cameras or DNA.

"Of course there have to be safeguards and built into this are very strong safeguards."

"Then the final argument is the cost," he said.

"And here I think there is a basic fact that is often left out of the equation.

"That is that biometric passports are going to be required anyway. The reality is biometric passports we are going to have to do irrespective of the identity base."

Blair said this would account for two thirds of the cost of the £5bn project.

"I think this is an argument about modernity," he concluded.

"In the end we have a modern world that we are living that has new and different types of crime.

"In the end if we don't use new technology, we will not be fighting crime effectively."

Earlier he wrote in the Telegraph newspaper that all non-EU immigrants will have to show an identity card in order to access jobs, public services or benefits.

"This will enable us, for the first time, to check accurately those coming into the country, their eligibility to work, for free hospital treatment or to claim benefits," he writes.

Blair said the change will come into effect with the start of the ID card scheme in 2008.

And he argued that opponents, including civil liberties campaigners and the Conservatives, are out of step with public opinion on the use of technology.

"It was very clear from last week's arguments about surveillance and the DNA database that the public, when anyone bothers to ask them, are overwhelmingly behind CCTV being used to catch or deter hooligans or DNA being used to track down those who have committed horrific crimes," he said.

"That's what surveys suggest, too, about their position on ID cards."