He'll be questioned about the relationship between Number 10 and the civil service.

BBC: Week ahead in committees

The prime minister has asked the head of the Civil Service to speed up the inquiry into the working relationship between Doctor Fox and his friend, Adam Werritty, who has business interests in the defence industry.

BBC: 'Smear and innuendo' against Fox

The chancellor's department has asked the Senior Salaries Review Body (SSRB) to review the relationship between judicial salaries and those of the senior civil service.

BBC: Irvine's role under fire