British secret agents who bugged the Pakistani high commission in London also helped themselves to confidential codes used by diplomats to send secret messages back to Islamabad, rediff.com has been told.

The decision to also tap the high commission's internal telephone system and place a camera inside the office of then high commissioner Abdel-Kader Jaffer was all part of the same operation.

It all went horribly wrong when a building contractor, who was working within the building and who had decided to tip off Britain's MI5 internal security agents about how they could gain access to the high commission, suddenly got cold feet.

The contractor, code named Notation, was paid £61,000 by MI5 in return for assisting them to enter the high commission building where he was helping with some refurbishment work.

However, he eventually decided to spill the beans to the Pakistanis.

Last week, the Sunday Times newspaper published his confession without naming the diplomatic mission involved. rediff.com later identified it as the Pakistani high commission.

Last week, rediff.com revealed how the UK's high commissioner to Pakistan was summoned to the foreign ministry in Islamabad to be asked if Prime Minister Tony Blair had personally authorised the operation.

The embarrassed British have responded by hinting that so-called rogue elements within the MI5's 'A' branch may have been responsible for the bugging exercise, which did not have the approval of ministers, including Home Secretary David Blunkett.