SINN Féin has said it does not support a public inquiry into the Renewable Heat Incentive (RHI) scandal because it would take too long and cost too much money.

As Stormont's opposition parties continue to call for a public inquiry into First Minister Arlene Foster's oversight of the botched green energy scheme, the DUP's partners in government have said they do not regard this as the best option.

Previously, Sinn Féin deputy leader Mary Lou McDonald called for a "public inquiry as a matter of urgency", while Newry and Armagh MLA Conor Murphy said a public inquiry should be one of the options considered to find out what went wrong with the RHI.

However, a statement issued by Sinn Féin on Friday night indicated that it no longer regards a public inquiry as necessary.

A party spokesman said its priority was "restoring public confidence in the institutions by holding those responsible for this scandal to account".

"We believe that this can be best achieved by an independent, time-framed, robust and transparent investigation undertaken by an independent judicial figure from outside this jurisdiction and appointed by the attorney general," a party statement said.

"It is Sinn Féin’s view that a statutory public inquiry could drag on for years at a significant cost to the tax payers and adding to the cost of this scandal."

The spokesman said the party was clear in its desire for Mrs Foster to step aside.

But SDLP leader Colum Eastwood said his party would resist "any attempts to push this into a back office or merely conduct a superficial review" of the scheme.

"The ongoing damage caused by this fiasco to public confidence in the assembly must be brought to an end and this can only be done by the immediate establishment of a public inquiry with full powers to compel witnesses and evidence," he said.

"The scale of the damage already inflicted, and the loss of staggering sums of taxpayers money demands that any investigation must be public, thorough and transparent."

Video: Arlene Foster speaking to the Irish News in October about RHI

Meanwhile, one of Mrs Foster's ministerial colleagues has claimed political rivals calling for her resignation as Stormont First Minister are more interested in a scalp than the truth.

Stormont Economy minister and fellow DUP member Simon Hamilton defended his party leader after a renewed wave of calls for her to step aside over her handling of a botched green energy scheme.

He accused opposition MLAs attacking the DUP leader over the Renewable Heat Incentive (RHI) scandal of offering nothing more than "party political attacks and resignation calls".

"On the one hand they call for a process to establish the facts but they have already decided what the outcome should be," he said on Friday night.

Mr Hamilton was reacting to the publication of a letter Mrs Foster sent to bankers about the RHI when she was economy minister in January 2013.

Mr Hamilton, who issued a statement through the DUP, not his department, said Mrs Foster wrote the letter before the fatal weaknesses in the scheme came to light.

"These letters, issued in 2013, once again highlight the fact that there was a significant underspend in the early years of the RHI scheme and far from highlighting an awareness of the issues which have subsequently come to light, further reinforce the fact that the department was operating, at that time, under a serious misapprehension about the scheme," he said.

He added: "Had the scheme operated as described in the letter then the present problems would not exist.

"The DUP supports an investigation which can be entirely free from political interference and which can report speedily in order to assist public confidence."