THE Commons authorities are hunting a mole who is trying to sell the expenses records of all MPs for £300,000, it was revealed last night.

The search has been launched after highly embarrassing details became public of Home Secretary Jacqui Smith’s parliamentary allowance claims – which included adult films watched at her home.

Middlesbrough MP Sir Stuart Bell, a member of the ruling Commons Commission, told BBC2’s Newsnight: “All of the receipts of 650-odd MPs... are for sale at a price of £300,000, so I am told.

“The price is going up because of the interest in the subject.”

Asked who was trying to sell the information, Sir Stuart said: “Well we have a pretty good idea of not the person, but the source, and that is a subject of a House of Commons investigation.”

News of the hunt emerged after official figures released by the Commons showed the total bill for MPs’ expenses rose by about six per cent last year, to just over £93m.

The latest breakdown of parliamentary allowances revealed that more than 150 MPs – almost one in four – claimed the maximum £23,083 under the controversial “second home” allowance.

For the first time, the breakdown also showed that at least 120 MPs claimed more than £1,000 – and some as much as £5,000 – from the taxpayer for their spouses’ travel to and from Westminster.

The figures were released as Gordon Brown attempted to defuse the row over Ms Smith’s political future, by insisting her £10 expense claim for two adult films watched by her husband was “a personal matter”.

However, the Home Secretary is still facing an investigation by the parliamentary authorities over her claim for at least £116,000 in secondhome allowances for the family home in Worcestershire.

At the weekend, it was revealed those claims included more than £1,100 for widescreen TVs, DVD players and digital set-top boxes, plus £1,000 for an antique fireplace and £550 for a stone kitchen sink.

Yesterday’s figures revealed Ms Smith claimed £22,948 for her “second home” last year, while classifying her sister’s spare bedroom in London as her main residence.

Some Labour MPs believe her authority is fatally damaged – and she was confronted by reporters shouting “Are you resigning?” when she left home yesterday.

Employment Minister Tony McNulty is also being investigated after claiming £60,000 for a “second home” lived in by his parents – eight miles from his own west London home.

Against that backdrop, the latest expenses breakdown – plus an announcement that MPs’ pay will rise tomorrow by 2.33 per cent, to £64,766 – could not have come at a worse time for the Government.

The highest claim for 2007-8 was made by Falkirk MP Eric Joyce (£187,371), with the smallest (£47,737) lodged by Philip Hollobone, MP for Kettering, in Northamptonshire.

Within the North-East and North Yorkshire, the largest claim was by Phil Willis (£167,561), followed by Nick Brown (£165,315), Sharon Hodgson (£164,038) and Hugh Bayley (£163,319).

Yesterday’s figures revealed that three-quarters of the region’s MPs claimed more than £20,000 under the second home allowance.

It includes purchases from the now-notorious “John Lewis list” – based on prices at the department store – allowing a £10,000 claim for a kitchen, £6,000 for a bathroom, plasma TVs and other electricals, and furniture.

Yesterday, attention also focused on MPs’ travel expenses which, for the first time, included details of up to 30 single journeys a year for spouses or children.

Among the higher claims for spouses’ travel were those of Sir Stuart Bell (£4,095), Hilary Armstrong (£3,703), Bill Etherington (£3,080) and Ms Hodgson (£2,880).

The least costly local MP overall was Phil Wilson (£117,268), followed by Chris Mullin (£129,581) and John Greenway (£130,967).

In total, MPs’ allowances claims passed £92.9m in 2007- 8 – up from £87.6m in the previous 12 months. The average figure was £144,176.

Gordon Brown claimed £17,073 in “second home” expenses – although he lives in No 10 for free. Tory leader David Cameron claimed £19,626 and Liberal Democrat leader Nick Clegg £23,083.

Last night, to head off the growing furore, the Prime Minister proposed scrapping the second home allowance altogether, to be replaced by a nightly allowance.

He also asked Parliament’s sleaze watchdog to speed up its inquiry into cleaning up MPs’ expenses.

A spokeswoman for the Committee on Standards in Public Life said members were minded to support Mr Brown’s request, although they were concerned not to repeat the previous mistakes of over-hasty piecemeal changes. A formal announcement is expected today.

Mr Brown also announced that ministerial pay would be frozen. Mr Cameron and Mr Clegg went further, deciding not to accept their 2.33 per cent pay rise.

But yesterday’s row is only a taster for the release, probably in summer, of the detailed receipts of three years of expenses’ claims by every MP.