David Kelly's widow, Janice, summoned Geoff Hoon, the Defence Secretary, to see her yesterday to demand an explanation of his role in the events leading to her husband's apparent suicide.
As the furore over whether the Defence Secretary and Downing Street colluded over the release of Dr Kelly's identity to the media showed no signs of abating, Mr Hoon spent almost 80 minutes at the family's home in Southmoor, Oxfordshire.
Fresh information passed to The Independent suggests Dr Kelly had close links to the espionage services, and was well placed to judge whether No 10 had exaggerated the threat posed by Saddam Hussein. It throws doubt on government comments before his death designed to portray him merely as a relatively junior technician.
Dr Kelly was a consultant to the Defence Intelligence Analysis Staff, which can draw upon classified information provided by the Secret Intelligence Service (MI6), MI5, GCHQ, military intelligence and material supplied by allied espionage services. In this capacity, he played an important role in providing information for the September Iraq arms dossier.
Dr Kelly, the country's leading expert on weapons of mass destruction, was asked by the Joint Intelligence Committee compiling the dossier to assess weapon-making material and equipment that the Iraqi regime could have been hiding, according to senior sources.
The scientist, who was found dead near his home six days ago, was used by MI6 to interrogate Iraqi defectors claiming to have information on Saddam's alleged weapons of mass destruction.
A Whitehall source said: "In reality, David Kelly's death means that the country has lost one of our most valuable analysts in the field of chemical and biological warfare. One only has to look at his work history to realise how extensive his contact has been with the world of intelligence."
Mr Hoon and Alastair Campbell, the Prime Minister's director of communications, have been accused of responsibility for Dr Kelly's identity being disclosed to the media. He was promised anonymity by the Ministry of Defence.
During yesterday's visit to Dr Kelly's family, Mr Hoon is reported to have expressed his sorrow over the scientist's death. Four days earlier, he had declared that he had no need to apologise.