The DUP's Simon Hamilton is the minister for the economy, which replaced Deti in May of last year

A STORMONT department has refused to release information relating to Arlene Foster's role in the botched Renewable Heat Incentive (RHI) scheme, claiming an investigation is ongoing and it would not be in the public interest to do so.

The Irish News requested all correspondence between the DUP leader and officials in the department for enterprise, trade and investment (Deti) on November 3 via a freedom of information request.

Earlier this week the Simon Hamilton's department for economy (which replaced Deti in May 2016) responded to the request, refusing to release the information.

In an email to The Irish News, the reason for the refusal was given as: the “public interest arguments” for withholding the information outweighed those in favour of disclosure and releasing it could prejudice an investigation.

However, an investigation has yet to be announced. DUP leader Arlene Foster said a minister from her party would release details about a public inquiry but this has yet to happen.

Failures in the implementation of the RHI scheme are set to cost an estimated £490 million of public money over the next 20 years.

Hopes of a swift inquiry into the scheme were all but dashed on Monday following the resignation of deputy first minister Martin McGuinness and the subsequent collapse of the executive, signalling the high probability of a snap election.

Ulster Unionist leader Mike Nesbitt lambasted the department's refusal to release the information.

"On the first point, if the matter is under investigation, it is clearly an internal investigation, and the public will have no knowledge of or confidence in such an investigation," he said.

"As to their other explanation for non-disclosure, the logic of their argument is that knowledge of the facts would prejudice establishing the truth.

"This is simply ridiculous and scraping the bottom of the barrel of excuses."

SDLP leader Colum Eastwood said the refusal cemented the need for a public inquiry.

"The selective release of documents under Simon Hamilton is exactly why we need a fully empowered public inquiry to deal with this fiasco," he said.

"Under DUP stewardship this department has drip fed those documents that it wants in the public domain while withholding others. That cannot be in the public interest.

"All parties should say clearly that they are committed to a public inquiry with full powers to compel papers and people under complete public scrutiny. That is the highest standard of transparency and accountability and should be progressed immediately."