Julie Kirkbride was facing new questions over allowances after it emerged that she employs her sister as a secretary even though she lives more than 100 miles from her constituency.

The Conservative MP says that she pays Karen Leadley, who lives in Dorset, £12,000 a year to answer letters from her constituents in Bromsgrove, Worcestershire. Tory party sources defended the arrangement and said that Ms Kirkbride could prove that Ms Leadley carried out work on her behalf.

Ms Kirkbride is already under intense scrutiny after Andrew MacKay, her husband, was forced to stand down as an aide to David Cameron. Mr MacKay claimed second-home expenses of £23,000 a year on his London address despite not having a property in his Bracknell constituency.

Mr Mackay has announced that he will stand down at the next general election, although Ms Kirkbride has not followed his move and insists that she has done nothing wrong.

She said that the employment of her sister, who works from her home in Wimborne, had been registered for some time and that Ms Leadley was a popular member of staff.

Ms Kirkbride said: “My sister does work for me on a part-time salary of around £12,000. She lives in Wimborne, Dorset, but she has a computer which is networked to my constituency office and London office.

“She carries out tasks on a regular basis but her principal job is to do constituency correspondence during the parliamentary recess and many people have written to say how helpful she has been.”

It emerged this week that Ms Kirkbride’s brother Ian bought about £1,000 of electrical equipment using her parliamentary office expense account. Ms Kirkbride said he found items on the internet at the cheapest price and they were “entirely in relation to my parliamentary duties”.

Friends of James Purnell have defended his use of taxpayers’ money to buy 3,000 fridge magnets. The Work and Pensions Secretary spent about £250 from an allowance designed to meet office costs on the magnets. A source close to Mr Purnell said the magnets were intended to publicise his website. “I’m not sure it was the greatest innovation in political communication but it was a legitimate claim,” he said.

A spokesperson for Mr Purnell said: “All office cost claims that James made and were paid out were in accordance with Fees Office guidance at the time and he made no personal gain. However, James shares the public anger at an expenses regime that seems completely broken and he agrees the whole system needs urgent and radical reform.”

David Cameron broke the unofficial truce on criticising expenses claims of opposition MPs when he said that claims for accountancy costs “beggar belief”.

Alistair Darling, the Chancellor, is among ministers found to have used an allowance for help filling in his tax return. A spokeswoman denied that he had claimed for any accountancy work not related to his activities as an MP.

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