THE police and MI5 have foiled at least thirteen suspected international terrorist plots in Britain in the past six years, security sources have told The Times.

To cope with the terrorist threat, Dame Eliza Manningham-Buller, the Director-General of MI5, has now switched another ?16 million of her annual budget of ?200 million towards fighting international terrorism. A record 87 per cent of the MI5 budget is now spent on counter-terrorism.

The thirteen foiled suspected international terrorist plots include one in November 2000, four in 2003, two in 2004, four in 2005 and two this year. The suspected plots this year do not include the police raid in Forest Gate, East London, conducted on June 2 after an intelligence tip-off raised fears that there was a chemical device in a house. Nothing was found.

The suspected plots also do not include a mass of overheard and uncovered conspiracies still in full flow with which the security services are trying to keep pace as more intelligence is gleaned daily.

During a meeting in May with relatives of the victims of the July 7, 2005, suicide bombings, John Reid, the Home Secretary, revealed that there were about twenty ?major conspiracies? by Islamic terrorists being monitored by the security services.

Mr Reid will highlight the terrorism dangers when he claims in a speech today that Britain is facing the most sustained period of severe threat since the end of the Second World War.

In a speech to the Demos think-tank, he will say that, while the security services will deliver 100 per cent effort and dedication, they cannot guarantee 100 per cent success in the fight against terrorism.

Mr Reid will call for a common effort from all sections of society as the only way of assuring the country?s common security. The current terrorist threat alert status is ?severe?, the second-highest grading.

?Our security forces and the apparatus of the State provide a very necessary condition for defeating terrorism but can never be sufficient to do so on their own,? Mr Reid will say.

Nine of the 13 suspected plots were foiled between 2000 and the suicide bombings in London last year. The suspected plots that were uncovered this year by MI5 and the police were foiled in May and June.

In May a number of Libyans were arrested, mainly in Manchester, suspected of being involved in the facilitation of terrorist activity overseas. They were detained under immigration laws pending deportation to Libya.

In June four individuals were arrested on suspicion of being linked to an al-Qaeda cell in Canada.

The other suspected plots include two that will come before the courts this year or early next year.