The foreign diplomatic mission where the United Kingdom's security services tried to plant listening devices is believed to have belonged to Pakistan.

The attempt was exposed by the Sunday Times newspaper, which quoted the codename of an English agent who was asked to facilitate access to the telephone system, visa room and cipher room of the high commission.

Although the front-page report refused to name the mission, it dropped a number of clues, including a description of the naval attaché's office on the top floor of the building and the visa office in the basement.

The report has embarrassed the governments of Britain and Pakistan, which on paper at least are allies with the United States in the fight against terrorism. According to the paper the US embassy in London was also party to the operation.

Such espionage has not been in evidence since the days of the Cold War, when electronic devices were attached to every nook and cranny of the embassies of the Soviet Union and its allies.

The decision to turn the spotlight on Pakistan seems to have been prompted by an awareness that many UK-based Islamic radicals of Pakistani origin have joined the Al Qaeda, either in the border regions of Afghanistan or other hotspots in West Asia.

What is also revealing is how little the Pakistanis are trusted by their UK counterparts and how for all the bonhomie that exists at official levels, a question mark hangs over President Pervez Musharraf's true intentions and his decision to distance himself from Islamic radicals.

The exposure is also a blow to the prestige of Pakistan's newly arrived high commissioner, Dr Maleeha Lodhi, who presented her credentials to Queen Elizabeth II only last Tuesday.

This week Dr Lodhi will host her country's Foreign Minister Khursheed Kasuri, who is believed to have extended his stay to find out details of the operation.

The report said the task of facilitating the bugging operation was given to a former MI5 (the UK's equivalent of the IB) agent, codenamed Notation, who has since confessed his role in the operation to the high commission. "It is likely that the foreign office will now have the embarrassing task of explaining the espionage operation to its ally," the report said.

It further claims that the MI5 took detailed plans and photographs of the mission before working out how to plant bugs in the telephone system and inside a closed-circuit television camera in the office of a diplomat. One officer is even alleged to have pretended to carry out a search for hazardous materials to gain access to secure areas.

Meanwhile, agent Notation received tens of thousands of pounds as cash payment from MI5. He was, according to the Sunday Times, also told by his handler that the entire operation had been authorised at the highest level with warrants being signed by Home secretary David Blunkett.