Boris Johnson could face 100 rivals in the contest for one of the safest Tory seats in London.
Conservative party HQ is expected to seek 'expressions of interest' later this week from candidates hoping to be selected in Uxbridge and South Ruislip.
The current MP, John Randall, who is retiring at the general election, had a majority of more than 11,000.
The local Conservative association has been told by party bosses to expect as many as 100 applications.
A shortlist is expected to be drawn up early next month before local party members choose their new Prospective Parliamentary Candidate on September 12th.