8216;Great8217; terror plot brewing in UK: Top official

8220;We have done all the things that we need to do, but the threat is building 8211; the complex plots are building,8221; West told the House of Lords, without elaborating.

His warning came soon after the House of Lords rejected a controversial security measure to extend detention without trial for terror suspects to 42 days. The counter-terrorism provision was in the pipeline after suicide bombers killed 52 rush-hour commuters in London in July 2005.

8220;The threat is huge. It dipped slightly and is now rising again within the context of 8216;severe'8221;, he was quoted as saying by the 8216;Daily Telegraph8217;.

British Home Secretary Jacqui Smith dropped the counter-terrorism measure after it was rejected in the upper house but warned critics they were exposing the country to a greater risk.

The British daily reported two weeks ago that security sources believed terrorist activity was nearing 8220;critical8221;.

The threat level is at the 8220;severe end of severe8221; according to sources who say the level of 8220;ambient activity8221; among terrorist cells has increased in recent months and they are now operating at full stretch.

Counter-terrorism officials are particularly worried by a growing threat from within the Algerian, Somali and Yemeni communities in Britain along with the established threat from youths returning from the al-Qaeda heartlands on the Pakistan-Afghan border, the report said.