Britain will undertake an immediate review of recruitment of staff for the National Health Service and expand background checks of highly-skilled immigrant workers in the wake of the failed car bomb attacks linked to migrant doctors, Prime Minister Gordon Brown said on Wednesday.

"As a result of what has happened in the National Health Service, I have asked Lord West, the new Terrorism Minister, to conduct an immediate review as to what arrangements we must make in relation to the recruitment," Brown said during question hour in the House of Commons.

"We'll expand the background checks that have been done where there are highly skilled migrant workers coming into this country," Brown said in his first appearance at the weekly PM's questions.

He said it was vitally important that the "message is sent out to the rest of the world that we will stand strong, steadfast and united in the face of terror."

He said the sponsors of skilled workers would be asked for background checks on them.

Among other measures, a watch list of potential suspects would be expanded to warn authorities across the world, and the admissibility of intercept evidence in court would be reviewed.

Two Mercedes cars containing petrol, gas cylinders and nails were found, one outside a nightclub in London's [Images] Haymarket and the other a little distance away last Friday.

The next day a green Jeep Cherokee loaded with gas cylinders crashed into the doors of Glasgow Airport's main terminal and burst into flames.

Seven of the eight persons arrested in worldwide inquiry into the terror plot are believed to be doctors or medical students.