Social Security chiefs have asked Sinn Fein to pay back benefits claimed by one of its councillors, it has emerged.
But a DUP MP claimed Sinn Fein has not yet returned the outstanding amount, estimated at £19,000.
Sammy Wilson, who has asked the fraud unit of the Social Security Agency (SSA) to investigate benefit claims by all Sinn Fein councillors, insisted: "The political party should refund the public purse.
"SF has no shame in exploiting our welfare system. Their councillors are paid allowances that go to the party and then the party expect the state to pick up the living expenses of the councillors in welfare benefits."
Sinn Fein branded Mr Wilson's demand for an inquiry as "disgraceful" and insisted all its representatives paid the same taxes as every other citizen - declaring all expenses and allowances to the Inland Revenue.
As the Belfast Telegraph revealed last month, Mr Wilson asked his party colleague, Social Development Minister Mervyn Storey, to initiate the probe.
His call came after a Sinn Fein Derry City and Strabane councillor Colin 'Colly' Kelly was acquitted on charges alleging he committed £19,000 benefits fraud over more than three years.
Mr Kelly said it had been an "honest mistake" and that as soon as he became aware of the situation, he had taken steps to rectify it.
In his court decision, Deputy District Judge Brian Archer said "maybe the political party should refund the public purse" because it had received the benefits of Mr Kelly's earnings as a councillor.
Yesterday the Department of Social Development said: "The Social Security Agency can confirm it has written to Sinn Fein asking for the party's views in terms of its intention to return the overpayments arising in this case."
Ex-Finance Minister Mr Wilson said: "I welcome the news that the SSA has requested that the outstanding debt is paid by Sinn Fein. Although, I understand that there has been no response.
"Sinn Fein should not be allowed to dodge this issue."
A Sinn Fein official responded: "Neither councillor Colly Kelly or Sinn Fein have received any correspondence from the Social Security Agency. Colly Kelly was acquitted and Sinn Fein was not before the court.
"Sammy Wilson's allegations are scurrilous and entirely without foundation. We will not take any lectures from Sammy Wilson or members of the DUP on openness or transparency."