It has been reported that Sinn Féin's five MPs have received nearly £500,000 in second home allowances, despite not taking up their seats at Westminster.
Details of their expense claims were published in the Sunday Telegraph newspaper.
In response, Sinn Féin said all its claims were legitimate and its MPs travel to London on parliamentary business and use the accommodation they rent.
The five have been implicated in an ongoing row in London about MPs' expenses, arising from the newspaper's publishing previously secret details of the claims made by many high-profile politicians.
They include former British Prime Minister Tony Blair, ex-Trade Secretary Stephen Byers, Cabinet Office minister Tom Watson and former Tory minister John Gummer.
Former Archbishop of Canterbury Lord Carey warned that a 'culture of abuse' had developed in relation to Westminster expenses, and MPs only had themselves to blame.
Some of those named in the newspaper's reports are said to be threatening legal action for supposed inaccuracies.
Parliamentary officials have asked Scotland Yard to investigate how the expenses details were leaked, but police sources indicated the force was unlikely to decide whether to launch a probe until after the weekend.
There have been widespread calls for the House authorities to disclose all the material now rather than allow the 'drip drip' disclosure by the Telegraph to continue.
