Odette Nightingale, presented by the paper as a "God-fearing Sunday school teacher" who had been left distraught by the experience, was paid between £25,000 and £30,000 by the newspaper, according to NoW sources.
A tape recorder hidden in Ms Nightingale's handbag captured Mr Spring's damaging remarks about the Royal family and fellow politicians, including John Major and his wife Norma.
Lord Wyatt of Weeford, NoW's political columnist, last week attacked the decision to publish the story, and called for a privacy law to restrict his own newspaper's exposs of politicians' lives.
Ms Nightingale said last week that her boyfriend, Chris Holmes, a City pension fund manager, had suggested sharing a bed with Mr Spring, the Parliamentary private secretary to Sir Patrick Mayhew, the Secretary of State for Northern Ireland, several times before she went to the MP's house. She eventually went to bed with him and Mr Holmes after a private dinner party.
Sources inside the NoW said approaches had been made on her behalf to the paper before the party, and as a result, Ms Nightingale had kept a tape recorder in her handbag during the dinner table conversation. But when the three moved to the bedroom, the recording was barely audible, so hi-technology tape enhancement techniques were used to present Mr Spring with "incontrovertible evidence".
Piers Morgan, NoW's editor, declined to comment yesterday, as did Mr Spring. Neither Ms Nightingale nor Mr Holmes was available.
On Friday, John Wakeham, chairman of the Press Complaints Commission, will announce the make-up of a higher profile, heavier hitting Press Complaints Commission: he hopes that "a slightly higher-powered commission than we've had in the past, with some well-known names, will add to public confidence".
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