Sinn Féin says the Government is neglecting its responsibility to taxpayers by failing to fully investigate the sale of Nama's northern loan book.

Last night, a BBC Spotlight programme alleged businessman, Frank Cushnahan, who has been at the centre of the £1bn Nama deal controversy, claimed last year that he was due to be paid a "fixer fee" in relation to the transaction.

The alleged statement is made on a covert recording made by the BBC's Spotlight programme.

Mr Cushnahan, who had served on Nama's Northern Ireland Advisory Committee, has consistently denied that he was due to receive money.

Sinn Féin President Gerry Adams says the Government has so far refused to launch an investigation into the sale.

He said: "They said 'there's nothing to see here, move on', but there is, clearly, and that was highlighted again by the individual who made some very, very, clear revelations.

"The hugeness of the money involved - and it's your money, it's the taxpayers' money - and this body was tasked to make sure citizens got the best value and the Government has a responsibility to oversee that."