Cameron's sister-in-law employed in his office

LONDON (Reuters) - The sister-in-law of Conservative Party leader David Cameron works on a part-time basis in his correspondence office, the party said on Saturday.

The disclosure comes a day after the opposition leader called for greater disclosure on the number of party MPs whose relatives work as members of their personal staff.

The call came in the wake of the scandal surrounding Tory MP Derek Conway who paid his son nearly 50,000 pounds of taxpayers' money for work he apparently never carried out.

Alice Sheffield works three days a week as a correspondence secretary in Cameron's private office.

She is part of a team of four full-time and two part-time staff in the Correspondence Unit, and is not employed directly by Cameron.

Instead, she is employed by Conservative Campaign Headquarters, a party spokesman said in a statement.

"Alice works 3 days per week on a standard correspondence secretary salary, which is paid on a pro-rata basis," the statement added.

"The salary for a full-time correspondence secretary in 2007 was 25,700 pounds."

More than 70 Conservative MPs employ relatives as members of their personal staff, Cameron said on Friday.