Steve Hilton, a former employee of the advertising agency Saatchi & Saatchi, is an old friend of the Tory leader and gets a monthly fee as a consultant to the party.

However, party insiders insisted last night that the arrangement was “transitional” while he was freeing himself of his business interests and that he would soon be joining the regular payroll.

According to company documents the party is paying £23,000 a month to Hilton’s marketing agency Good Business for his services.

The amount of his salary reflects how valued Hilton is by the Cameron team. He is credited with masterminding the Conservative leader’s successful comeback after he faltered in the leadership contest in the summer, and his brilliant speech — without notes — to the conference in the autumn that turned around his fortunes and saw off the challenge of the rightwinger David Davis.

He has been likened to Labour’s Peter Mandelson and Alastair Campbell in his talent for political strategy.

The Conservative party calculated his fee by adding the £100,000 salary he received last year to the £176,000 dividend he got from his shareholding in Good Business.

The total was then divided into 12 monthly instalments. Being paid at that level makes him the highest paid adviser in the history of the Conservative party.

A spokesman for Cameron said: “We are in a transitional period whereby Steve Hilton is still in the process of working part-time for Good Business and for the Conservative party. Shortly he will be joining us full time and will be paid by the party as an employee.”

Hilton, the son of Hungarian immigrants, went to Oxford University.

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