Channel 4's Dispatches receives a list of landlords renting to around 300 MPs who are claiming rent payments on expenses, as Equalities Minister Helen Grant is forced to defend her arrangement.
The new investigation into MPs' expenses comes more than two years after new rules came in, banning MPs claiming expenses for mortgages but still allowing them to claim for rent.
Taxpayers are still contributing around £89m on MPs expenses compared with the £90m before the last expenses scandal broke. There are now more than 300 MPs claiming rent, costing the taxpayer more than a £1m a year.
Dispatches reporter Antony Barnett told Channel 4 News: "We wanted to know who MPs are renting from, we knew there were more than 300 claiming rent expenses but didn't have any details."
The programme looks in detail at MPs found to have rented out property, then put in a claim for renting another home.
"Their expense claims fall within the rules but our programme asks whether they're in the spirit too," he added.
On Monday, Dispatches received a list of landlords renting to around 300 MPs who are claiming this on expenses. It is is the first time this list has been published and follows a battle with the parliamentary authorities following a Freedom of Information request was initially stalled by an intervention from Commons' Speaker John Bercow.
Equalities Minister Helen Grant has been forced to defend claiming the maximum expenses for a second home in London despite living just 19 miles from the Commons.
Mrs Grant, appointed to the Ministry of Justice in September's reshuffle, lives in a £1.8m home in Reigate, Surrey - outside her Maidstone constituency. She also rents a Thameside flat near the MI6 building in Vauxhall which is funded on expenses
Channel 4's Dispatches will reveal:
Cabinet Office Minister Francis Maude is still claiming thousands of pounds on a second home in central London despite the prime minister's personal pledge Maude would not "claim any money" on his second home.
Equalities Minister Helen Grant is claiming £20,000 a year for a luxury London flat despite owning a £1.8m home in Surrey just 19 miles away from Westminster.
Treasury Minister David Gauke recently sold his second home in central London which the taxpayer helped buy and has kept a profit of more than £20,000.
John Whittingdale, chairman of the House of Commons Culture, Media and Sport select committee has moved out of a second home which the taxpayer helped fund and is renting it out for £400 a week. He is now claiming expenses for renting out a property nearby.
Mrs Grant is eligible for a second home allowance because her constituency is outside London. The Independent Parliamentary Standards Authority (Ipsa) confirmed the MP's claim was within the rules.
A spokeswoman for the MP said: "Mrs Grant's constituency has been deemed by Ipsa to be a non-London constituency and she is therefore fully entitled to use her rental accommodation allowance either in London or in the constituency. She has a base in her constituency at her mother's property, where her son also lives, so she sees no need to rent a further property there. The focus of her time and responsibility has always been Maidstone and the Weald."
More from Channel 4 News: New MPs' expenses row
'Spirit of the rules'
But Matthew Sinclair, chief executive of the TaxPayers' Alliance, said the MP appeared to have breached the spirit of the rules.
"The taxpayer-funded allowance for a second home is meant to be there for MPs living in a constituency home from which they cannot reasonably commute to Westminster on a daily basis," he said.
"Most people would expect that by choosing to remain living in her Surrey home - which is a commutable distance from London - Mrs Grant would have made herself ineligible to make these claims.
"This is a loophole in the rules which ought to be closed."
Watch tonight at 8pm on Channel 4's Dispatches - MPs: Are they still at it?