LONDON – The threat of another major terrorist attack is building in Britain, a government security minister said Tuesday, a day after the House of Lords rejected a measure that would have extended the amount of time police can hold terror suspects without charge.

Alan West, a counterterrorism minister and member of the House of Lords, said the threat is rising after having dipped slightly.

“Another great plot is building up again that we are monitoring,” he said during a debate on the government's anti-terror legislation, without providing further details.

The Home Office, which oversees policing and security in Britain, refused to elaborate on West's comments.

“There are many plots, individuals and groups under investigation. We don't elaborate on specific plots or individuals,” the Home Office said in a statement.

On Monday, the House of Lords rejected a controversial government plan to extend the amount of time police can hold terror suspects without charge from 28 to 42 days.

The government's effort to strengthen counterterrorism provisions gathered pace after suicide bombers killed 52 rush-hour commuters in London in July 2005.

Opposition lawmakers branded West's comments reckless.

Chris Huhne, home affairs spokesman for the Liberal Democrats, said West's comments risked “blowing the cover” of a police counter-terrorist investigation.

Jonathan Evans, head of the security services, said in a speech last year that 2,000 individuals in Britain were considered a direct threat to national security because of their support for terrorism and warned that there could be thousands more the authorities did not know about.

The current threat level in Britain is assessed as severe – the second highest of five possible ratings.