His appointment by Diligence, which employs several former members of the SAS and SBS, is the first job Mr Howard has accepted since he announced after the party’s defeat last year that he would not be contesting his seat at Folkestone & Hythe at the next election. Mr Howard, who is expected to be paid a six-figure salary, told The Times that he had been contracted to work a minimum of half a day a week, and insisted that it would not interfere with his constituency duties.

In the next two weeks he is expected to announce more non-executive directorships, although he declined to say in what field those would be.

Diligence was set up six years ago by its chief executive, Nick Day, a former MI5 agent who also served in the SBS. His two co-founders, neither of whom still works with the firm, were former CIA and Soviet military intelligence agents.

The company, based in New York, is headed by Richard Burt, a former US Ambassador to Germany, who was the chief arms control negotiator in the first Bush administration. Mr Howard, who will work out of Diligence’s new offices in Canary Wharf when he joins at the end of this month, said that the approach to join the company had come through Mr Burt. “What they do is very interesting and exciting and is just what I was looking for. A great deal of my experience and knowledge is relevent to what they do. There’s a growing need for intelligence gathering in this age of globalisation, with people having to deal with parts of the world which they may not be familiar with.”

Mr Howard held several Cabinet posts during his political career, including Home Secretary, Employment Secretary and Environment Secretary. He has also been Shadow Foreign Secretary and Shadow Chancellor.

Diligence is one of a growing number of firms that companies turn to when they want help with problems ranging from fraud, money laundering and personnel issues to physical security, threats to reputation and vetting potential partners overseas.

The world of corporate investigations was under the spotlight two years ago during the abortive bid by Sir Philip Green, the billionaire Bhs and Top Shop owner, for Marks & Spencer.

M&S claimed that a dirty tricks campaign against it was being assisted by corporate investigators, although the two firms named, Kroll and Control Risks, strongly denied that they had been involved in tapping into the phone records of Stuart Rose, the M&S chief executive. Sir Philip vehemently denied hiring investigators.

SPIES R US

Diligence is run by chief executive Nick Day, a former MI5 agent and SBS officer who was senior investigator with Maxima Group, the fraud investigations firm. The senior advisory board includes William Webster, a judge and former Director of the CIA and the FBI, and Lord Powell of Bayswater, former Private Secretary to Margaret Thatcher and John Major. Last July it raised $15 million (£8 million) for expansion by selling a majority stake to a buyout fund founded by the Latin American financier Juan Navarro.

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