Top Tory Chris Grayling has claimed £104,183 of taxpayers’ money over six years for a London flat – even though he has a family home just 17 miles away from Westminster.

And neighbours of the Shadow Home Secretary say they “rarely, if ever” see him at the Westminster flat where his postbox is packed with unopened mail.

On the eve of becoming an MP in June 2001, Mr Grayling, 46, paid £127,000 for the one-bedroom flat in a six-storey block, which has views of Westminster Cathedral and is only a short stroll from the House of Commons.

But a local estate agent said the value of properties in the block had soared to between £210,000 and £330,000, despite the recession.

Our inquiry sparked claims from MPs last night that Mr Grayling  would trouser a huge profit from the London property market,  largely thanks to taxpayers’ cash.

Under Parliamentary rules, Mr Grayling is allowed to use his additional costs allowance (ACA) to pay for and furnish a second home – either in London or his constituency of Epsom and Ewell.

Between 2001 and 2007, he claimed a total of £104,183 under the ACA - close to the maximum possible claim over the period of £122,710.

But the £1.5million family home he shares with wife Sue and their two children is just 16.9 miles from Westminster in Surrey’s prosperous commuter belt. He bought the imposing house with its sweeping drive and grounds in Ashtead for £680,000 in 2000.

Last night, campaigning Lib Dem MP Norman Baker attacked Mr Grayling’s use of taxpayers’ cash, saying: “MPs get this allowance to help carry out their duties. It is not intended to make a capital gain on property.”

Our investigation will be a major embarrassment to David Cameron. He has insisted Tory MPs must obey the spirit, as well as the letter, of Parliament’s rules.

He said MPs should ask themselves if they could explain their expenses and housing arrangements “in a reasonable way to a reasonable person and would they think it is reasonable”.

Just days ago, the Tory leader attacked Home Secretary Jacqui Smith and said she had “questions to answer” after claiming £116,000 towards her family home in Worcestershire, insisting she spends more of her time at her sister’s house in South London.

Visitors to Mr Grayling’s flat saw his postbox stuffed full with mail last week. The man billed as Mr Cameron’s “attack dog” has also failed to replace a handle from the front door where there are two jagged holes.

One male neighbour, who did not wish to be named, said he had never seen Mr Grayling when shown a picture of the bald MP.

Another neighbour said: “I don’t know him at all. There is a light on occasionally, but he is not here very often.” And a woman from a flat beneath the MP’s said: “I have no idea who this man is.”

Mr Grayling insisted yesterday he had done nothing wrong. He said his claims were within the rules and that he used the flat “regularly” – but was not seen by anyone because he arrived late at night. He said: “The only reason I have it is because I’m working very late a lot of the time. I virtually never arrive before 11pm and I leave by 8am the next morning.

“I don’t use it as a postal address.  The post box is full of pizza leaflets. I only empty it when it gets full.

“I’m there regularly when I’m working late, which is every week.”

Mr Grayling’s £2.5m property empire also includes two terraced houses in Wimbledon, South West London, which are rented out.

vincent.moss@sundaymirror.co.uk