Questions have been raised after it emerged that an investigation into a DUP aide is being carried out by the department led by the minister he advises.
Stephen Brimstone is being examined over claims he breached a code of conduct after he was accused of political interference in the award of a public housing contract. If an initial examination leads to a formal probe, Social Development Minister Nelson McCausland's adviser could face disciplinary action, including suspension or even dismissal.
Lisburn DUP councillor Jenny Palmer told the BBC's Spotlight programme last month she had been put under pressure in a phone call from Mr Brimstone to change her vote at a Housing Executive board meeting.
It was considering a request from Mr McCausland to extend the Executive's contract with the Red Sky maintenance company. The £8m-a-year deal was terminated four months before the July 2011 meeting amid allegations of overcharging.
Mrs Palmer said Mr McCausland's adviser told her before the vote: "The party comes first – you do what you're told."
The advisers' code of conduct states that they "should not use official resources for party political activity".
Mr Brimstone challenged Mrs Palmer's account of the conversation. Last night questions were being asked after it was disclosed that an initial probe is being conducted by officials from Mr McCausland's own department.
Traditional Unionist leader Jim Allister said: "Given the powerful position which special advisers hold, I feel it would be better if complaints were examined by an individual or body completely independent of the department."