London: Britain is to allow one of its intelligence agencies to monitor all phone calls, texts, emails and online activities in the country to help tackle crime and militant attacks, the Interior Ministry said on Sunday.

"It is vital that police and security services are able to obtain communications data in certain circumstances to investigate serious crime and terrorism and to protect the public," a Home Office spokesman said.

The proposed law already has drawn strong criticism, from within the ruling Conservative Party's own ranks, as an invasion of privacy and personal rights.

"What the government hasn't explained is precisely why they intend to eavesdrop on all of us without even going to a judge for a warrant, which is what always used to happen," Member of Parliament David Davis told BBC News.

"It is an unnecessary extension of the ability of the state to snoop on ordinary people," he said. New legislation is expected to be announced in the legislative agenda-setting speech given by the queen in May.

Currently, British agencies can monitor calls and e-mails of specific individuals who may be under investigation after obtaining ministerial approval, but expanding that to all citizens is certain to enrage civil liberties campaigners.

Internet companies would be required to instal hardware which would allow the Government Communications Headquarters (GCHQ), referred to as Britain's electronic 'listening' agency, to gain real-time access to communications data.

The new law would not allow GCHQ to access the content of emails, calls or messages without a warrant, but it would allow it to trace who an individual or group was in contact with, how frequently they communicated and for how long.

The Sunday Times newspaper, which first reported the story, said some details of the proposals were given to members of the Britain's Internet Service Providers' Association last month.

"As set out in the Strategic Defence and Security Review we will legislate as soon as parliamentary time allows to ensure that the use of communications data is compatible with the government's approach to civil liberties," the Home Office spokesman said. Any proposed legislation changes are likely to face stiff opposition in both houses of the British Parliament.

A similar proposal was considered by the then-ruling Labour party in 2006 but was abandoned in the face of fierce opposition by the Conservatives and Liberal Democrats, who are junior partners in the ruling coalition.

The proposed legislation could reflect the U.S. Patriot Act, controversially introduced six weeks after September 11 in 2001, to expand the government's authority to monitor the communications activity of its citizens.