As further details emerged about MPs who employ relatives at the House of Commons, former Cabinet minister Peter Hain confirmed that his 80-year-old mother works part-time for him as a secretary.
Leading anti-apartheid activist Adelaine Hain has worked for her son at the Commons since 1991, earning £5,400 from Mr Hain's expenses last year.
But Neath MP Mr Hain insisted that there was no question that she did the work for which she was paid.
"I've never hidden anything," he said. "She works really hard, and that's that.
"She's been here since 1991 and everybody knows about it."
Mrs Hain provides "part-time secretarial assistance and cover for my offices", he said.
Leaders of all three parties have told their MPs to make clear if they employ members of their families.
Under parliamentary rules, there is no bar on employing relatives and many MPs recruit their spouses or children as secretaries.
Labour sources said it was believed between 90 and 95 of its MPs employ relatives, while Mr Cameron has said that 70 Tories do so and the Liberal Democrats said 12 of their MPs do - in total, more than a quarter of the Commons.
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