Michael Simmonds, the party's director of membership and marketing, is believed to have been told to leave Conservative Central Office (CCO) when he was summoned to a meeting with Michael Ancram, the party chairman, yesterday.
Mr Simmonds is a close political ally of Michael Portillo, the former cabinet minister, who has criticised Mr Hague's U-turn. He was regarded as a "rising star" by fellow Tory officials.
Friends said he was unhappy at last week's rejection of free-market solutions for education, health and welfare by Mr Hague and Peter Lilley, his deputy. "He is the first casualty of our civil war," one Tory insider told The Independent last night.
Mr Simmonds, who was not available for comment, played a key role in the 1997 general election campaign as political adviser to Brian Mawhinney, then party chairman, and his successor, Lord Parkinson, before taking over responsibility for membership involvement and marketing.
His departure followed a mole-hunt at CCO launched after it emerged that the first draft of Mr Lilley's controversial speech went even further in distancing the party from Baroness Thatcher's legacy.
The leaked draft showed that Mr Lilley had planned to say: "Most Conservatives have always accepted that the public services are intrinsically unsuited to delivery via the market." It also said "market processes have at best an auxiliary role to play" in providing health, education and welfare.
Mr Lilley watered down his speech - in which he said that the market had "only a limited role in improving public services" - after criticism from Shadow Cabinet colleagues. But the leak added to the controversy over Mr Hague's policy switch.
The party leadership sought to play down Mr Simmonds' departure last night, with sources close to Mr Hague saying it was "not the end of the world".
But Tory MPs were gloomy as the news spread at Westminster. One said Mr Hague's attempt to relaunch the party with a "caring" image on public services had backfired spectacularly by advertising Tory divisions ahead of next week's elections to local authorities and the Scottish and Welsh assemblies.
Tory headquarters said in a statement that Mr Simmonds had resigned his office. Mr Ancram said: "Michael Simmonds has given substantial and committed service to our party, for which I am grateful."
Mr Hague's allies insisted he would press on with his drive to reposition the party. "He is determined to get the message across that we are committed to the public services as predominantly taxpayer-funded organisations," one aide said.
Today, Labour will seek to exploit the Tory divisions, with three ministers claiming the Tories are still "lurching to the right" on policy despite Mr Hague's "warm words".Reuse content