Disgraced MP Iris Robinson is under police investigation after securing £50,000 from two developers to fund her toyboy lover's restaurant business, it was disclosed on Thursday.
Police in Belfast said their organised crime branch, which specialises in complex financial probes, had been called in to establish whether any criminal offence had been committed.
A statement said: "The investigation will be conducted in a thorough and professional manner as expeditiously as possible."
It added: "It will also be conducted with respect to the human rights of any person and in a manner that complies with the Police Service's duty to carry out impartial and independent investigations in compliance with our Code of Ethics."
Detective Chief Superintendent Roy McComb will head the inquiry.
Mrs Robinson, 60, was given £25,000 each from the two wealthy Northern Ireland property developers, Kenny Campbell and Fred Fraser, to help Kirk McCambley, 21, establish his business, the Lock Keeper's Inn on the banks of the river Lagan in south Belfast. She kept £5,000 for herself.
In the immediate aftermath of the sex and money scandal, mother-of-three Mrs Robinson, wife of the Northern Ireland First Minister Peter Robinson, announced she was resigning as MP for Strangford and from her membership of the Stormont Assembly.
She is currently undergoing acute psychiatric treatment after trying to kill herself last March when she confessed to her husband about her secret affair.
It has also emerged that Mrs Robinson lobbied for three planning applications on behalf of the two developers. Mr Fraser died last year. Mr McCambley has repaid £20,000 to Mr Campbell, but still owes £5,000. Mr Campbell has said he contributed between £4,000 and £5,000 to the DUP several years ago, but denied that he personally donated any money to Mrs Robinson or her husband.
Mr Robinson, who is already under investigation to establish if he broke his ministerial code of conduct and the pledge of office, has insisted he is confident his name will be cleared.
