The start of an inquiry into an ill-fated green energy scheme that triggered the collapse of power-sharing in Northern Ireland has been delayed.

The Renewable Heat Incentive probe being chaired by retired judge Patrick Coghlin, which had been due to open next month, will now commence hearings on 7 November.

Democratic Unionist leader and former first minister Arlene Foster, whose role in the scheme was at the heart of the political row that triggered the collapse of power-sharing at Stormont, is not anticipated to give evidence until the new year.

Sinn Féin has repeatedly indicated its unwillingness to return to any coalition government with Ms Foster as first minister until her actions related to the RHI are examined by the inquiry.

Mr Coghlin outlined the revised timetable at the latest preliminary hearing of the inquiry at Stormont.

The volume of evidence being examined - now standing at 880,000 pages - was one of reasons he cited for the delay in commencing formal hearings.

"Clearly it is a mammoth task to review and assimilate this documentation," he said.

The state-funded RHI was established to incentivise businesses to shift to renewable energy sources by offering a proportion of the costs to run eco-friendly boilers.

But in Northern Ireland the subsidy tariffs were set too high and without a cap, so it ended up paying out significantly more than the price of fuel.

This effectively enabled some applicants to "burn to earn" - getting free heat and making a profit as they did so.

Mrs Foster had a central role in establishing the scheme during her time as Stormont economy minister. She has insisted she acted correctly throughout.

Her refusal to accede to Sinn Féin's demand that she step aside as first minister pending the outcome of an inquiry prompted the late Martin McGuinness to resign as Sinn Féin deputy first minister in January, precipitating the collapse of power-sharing.

While the inquiry will broadly examine the RHI scheme on a chronological basis, it will also work up the line of responsibility in terms of witnesses, with junior ranking civil servants called first and permanent secretaries and ministers due at the end of the hearings.

The probe has served more than 470 notices compelling the production of evidence.

There are three core participants - Stormont's Department of the Economy, the British Department of Finance, and Ofgem, which administered the scheme.

Judge Coghlin said 23 other organisations and individuals had been granted enhanced participatory rights, including Mrs Foster and her successor as DUP economy minister, Jonathan Bell.

Those granted the status have the right to be legally represented in the proceedings.

A number of DUP party advisers, whose role in the scheme will also be scrutinised, have also been granted the enhanced status.

The inquiry chairman also announced that certain information would be redacted from public view during the probe - namely information of a commercially sensitive nature or evidence that might prejudice any potential future fraud inquiries.

The RHI inquiry team has had to take on significantly more staff than first envisaged to deal with the workload. It is understood an initial workforce of 10 has expanded to 35.

The inquiry will run on a three-week cycle of two weeks of oral hearings and a week of analytical and preparatory work.

The first week will be taken up with a lengthy opening statement from the legal counsel to the inquiry followed by opening statements