Two DUP MLAs have revealed that they have family members who installed Renewable Heating Incentive (RHI) boilers.

The news comes as Northern Ireland Economy minister Simon Hamilton said he had written to claimants to advise them that their details would be made public on Wednesday.

He was speaking as members of the Stormont Assembly voted in favour of his plan to mitigate the projected £490 million cost of the controversial Renewable Heat Incentive (RHI) scheme.

The so-called cash-for-ash scandal is one of the main reasons why Stormont collapsed. Mr Hamilton's amended legislation would reduce tariffs paid to about 1,800 people who got into the scheme before November 2015.

The total RHI spend in Northern Ireland is estimated at over £1 billion over the next 20 years.

The Treasury is set to cover £660 million of that, with Stormont landed with the remaining £490 million.

In a statement released on Monday night the DUP said: "Following an audit of all our MLAs in order to achieve transparency and to help build public confidence we asked every DUP MLAs to indicate whether any of their family members are beneficiaries in the RHI scheme.

"Carla Lockhart has indicated that her sister-in-law 'a (sic) husband is a farmer and is in the scheme. Carla has only recently become aware of this.

"William Irwin has a son-in-law who is a farmer and is in the scheme. Neither MLA was involved in lobbying for these individuals and neither has any financial or other interests in the farms concerned.

"We would again want to point out that in the main those in the non domestic RHI scheme applied absolutely legitimately to what was a government approved scheme and should be viewed as such."

On Saturday DUP MLA Jim Wells revealed that he has four family members, including a brother, who installed wood pellet boilers under the scheme.

During a debate about the amended regulations, Mr Hamilton told MLAs: "The house can support these regulations or they can permit up to £30 million to be lost to the Northern Ireland budget next year."

Mr Hamilton said he had taken "extensive legal advice" on his cost-cutting plan.

He also said that publishing the names of RHI claimants will reveal that members and supporters of many parties in the assembly have links to the initiative.

"It will show that it isn't just, as some would seek to portray it, DUP members or supporters that are benefiting from the scheme," the minister added.

Former DUP minister Jonathan Bell accused officials within the Economy Department of withholding information from him about the scheme.

Mr Bell, who succeeded Arlene Foster as minister at the Stormont department that set up RHI, told the Assembly that several of his requests for documents relating to the scheme have gone unanswered.

He claimed one of the documents was an email suggesting "DUP party officers interfered" in the scheme.

Using Assembly privilege, he claimed he had been told by other party members that a brother of one of the special advisers - Timothy Johnston - was installing the boilers.

The DUP immediately rubbished the claims. In a statement a party spokesman said: "For the avoidance of doubt, Timothy Johnston's brother does not, nor never has installed boilers, does not work in this sector and has not been involved in any RHI issues whatsoever. We challenge Mr Bell to produce a shred of evidence outside the chamber."

Last week, another special adviser (Spad) - former DUP director of communications John Robinson - stood aside after it emerged that his father-in-law runs two green energy boilers.

Leader of the Traditional Unionist Voice (TUV) party, Jim Allister, claimed that another ex-DUP Spad, Stephen Brimstone, "is heating his own house on the non-domestic (RHI) boiler scheme".

Using Assembly privilege, Mr Allister said Mr Brimstone had a new biomass boiler in his house - but took it out and installed a new non-domestic one to "rip off" RHI .

The DUP indicated that Mr Brimstone did not want to comment on Mr Allister's claims.

The draft Renewable Heat Incentive Scheme (Amendment) Regulations (Northern Ireland) 2017 was backed unopposed on an oral vote.

Mr Bell, who was suspended from the party in December for speaking to the press about the scandal without party permission, said he had been prevented from closing the RHI scheme by DUP special advisers.

The DUP rebel claimed a senior civil servant in the Economy Department told him that had the special advisers not interfered then the cost of the scheme could have been halved.

Mr Bell said he wrote to Arlene Foster in March last year to tell her that special advisers were advising that the scheme be kept open and to outline a number of difficulties.

Mr Bell added: "I have sought from the Department of Economy and the permanent secretary (Andrew McCormick) all the information that was made available to me as minister. I understood that a minister could see all the stuff that was there before.

"It is with regret I still haven't seen the information that was put before me as minister.

"It has been confirmed by the permanent secretary that there is an email in the system that says DUP party officers interfered in the process."

Mr Bell said that last week he asked the permanent secretary if he could see that information, but he has not received a reply.

"I'm not going to speculate as to why. Perhaps the judge (who will oversee a public inquiry into the scandal) will be able to give a more definitive answer."

He added: "You may hide information from me. You will not hide the information from a judge-led public inquiry."

Earlier the Ulster Unionist Party revealed that a business owned by an aunt and uncle of Sandra Overend MLA is a recipient under the RHI scheme. The party said Ms Overend was previously unaware of this.

Neil Somerville, who served as an Ulster Unionist MLA for seven months during the last mandate, before standing down, has a wood pellet boiler accredited under the RHI scheme in his family's business, Clogher Valley Horses Welcome.

Mr Somerville said: "We inquired about a wood pellet boiler in July 2015 and a 99kW boiler was installed in August 2015.

"The installation of the wood pellet boiler has meant that my wife is now able to carry out her work on a year-round basis and a horse solarium has been installed. We are happy for an inspection to take place."

Belfast Telegraph