A front-page report in the Mirror, alleging that Mr Cook had fired a secretary to make way for "his mistress Gaynor Regan", and reports claiming that the security service "stopped Cook hiring lover", forced the Foreign Secretary into a public denial.
Speaking at the end of a two-day visit to Brussels, Mr Cook said he wanted to "put the record straight".
Anne Bullen, the Foreign Office secretary whom he dismissed last May, had not been a career civil servant, but had been given her pounds 24,000, fixed- contract post by Douglas Hurd, then Foreign Secretary, in 1993.
Mr Cook suggested that Miss Bullen's appointment had been abnormal, and said she had been paid at an inappropriately high rate. "I reluctantly came to the conclusion that I could not extend her contract because she was impossible to work with. One option ... would have been to appoint Gaynor Regan, who had been my diary secretary for four years. I quickly decided not to pursue that option. I asked the Permanent Secretary to appoint a diary secretary ... through the normal procedures..."
But allegations made by Miss Bullen, 56, yesterday prompted Michael Howard, the shadow foreign secretary, to denounce Mr Cook, saying his credibility had been left "in tatters". He said: "Anne Bullen makes it clear she was sacked in order that Gaynor Regan could be appointed. This was a scandalous abuse of ministerial power." He later added a qualification - "if Anne Bullen's account is true".Reuse content