Ann Widdecombe, former Minister of State at the Home Office, is expected to write to the Leader of the Opposition, John Major, outlining her concerns about the way Mr Howard behaved while Home Secretary.
Ms Widdecombe and Mr Howard clashed over the sacking of Derek Lewis as director of the prison service in 1995 and she is expected to complain that Mr Howard's actions then ought to disqualify him from leading the party. Ms Widdecombe, a right-winger who is expected to back Peter Lilley in the leadership contest, was not available for comment.
Her expected intervention will boost the prospects of another leading candidate, William Hague, who has emerged as the choice of constituency activists to be the new leader of the Party.
A poll of local associations by Tory Central Office found "overwhelming" backing for the 36-year-old MP.
The votes in two regions were leaked to the Hague camp. In Wessex, he secured the support of 23 out of 33 constituency party chairmen and in the South- East he took nine of 23 votes.
Mr Hague plans to build on this support with a three-week tour of constituencies. His aides hope the local parties will put pressure on the 164 Tory MPs to vote for him.