Police are examining allegations of misuse of MLAs' expenses.
The PSNI has said officers from its serious crime branch were assessing the claims of "potential criminality".
The series of allegations against a number of Assembly members were outlined in two recent documentaries by BBC Northern Ireland Spotlight, the second aired last night.
The programmes shone particular focus on how representatives of the Assembly's two largest parties - the DUP and Sinn Fein - claimed money over the last decade.
They included an allegation that Sinn Fein MLAs drew down nearly £700,000 in expenses for research apparently conducted by a company run by the party's finance managers.
Sinn Fein said that its office cost allowance spent with Research Services Ireland had been exclusively for Assembly and constituency work.
It also reported claims of more than £4,000 worth of heating oil for one DUP MLA's office.
It was claimed in one year in the name of Willie Hay for his constituency office's heating oil.
Mr Hay's brother-in-law and former office manager has been suspended, according to Spotlight.
Willie Hay told the BBC he could not comment on the issue as it is now the subject of a police investigation.
Now, Alliance Party leader David Ford, has said that an external audit of MLAs' expenses is needed.
It comes after Spotlight reported on a series of MLA office expense claims in the first part of its investigation.
It raised concerns over how Sinn Fein and DUP figures in particular get an allowance of up to £70,000 a year.
Deputy First Minister Martin McGuinness, Mid Ulster MP Francie Molloy and other Sinn Fein representatives were accused of paying thousands of pounds in rent to cultural and historical societies which could not be shown to exist.
Mr McGuinness insisted his party had always been "above board" on expenses and had nothing to fear from a new audit.
The DUP MP Ian Paisley and Executive Minister Arlene Foster were also called into question over their constituency offices in Ballymena and Enniskillen.
The DUP has said no rules were broken.
In the programme - the first of the two-part investigation - the former chairman of a Westminster standards watchdog, Sir Alistair Graham, said there should be a detailed investigation into the allegations.
Justice Minister David Ford added his weight to demands for a full and independent probe "carried out in a way that prevents any political party from interfering or preventing the facts from coming out".