Loyalist Jamie Bryson is seeking to call the DUP's most powerful unelected figure as a defence witness in his NAMA conspiracy trial.
The loyalist has written to party chief executive Timothy Johnston asking him to give evidence in the case which is back before Belfast Magistrates Court on Tuesday.
He has asked Mr Johnston to indicate within a fortnight if he will "voluntarily attend court as a defence witness". If he won't, Mr Bryson said he would "have no other option than to seek a witness summons to compel you to attend".
The DUP last night declined to comment on the move by the loyalist.
Mr Bryson is also seeking any NAMA -related emails and other "electronic communications" that may be in Mr Johnston's possession. He has told the DUP chief executive that he could seek a third-party disclosure order in court for any material.
The loyalist sent his request bilingually. He said that given the DUP's "keenness on the Irish language and statutory protections", he thought it appropriate to have his correspondence translated into Irish "in the spirit of New Decade, New Approach".
Mr Bryson is charged with conspiracy to commit misconduct in public office alongside former Sinn Fein MLA Daithi McKay and party member Thomas O'Hara. He will appear before judge Fiona Bagnall today when a date will be set for the committal hearing.
He is representing himself in the potentially explosive trial.
The charges relate to his 2015 appearance before Stormont's Finance Committee, chaired by Mr McKay, which was investigating the sale of assets in Northern Ireland to a US investment fund by the National Asset Management Agency, the so-called bad bank created by the Irish government to deal with the toxic loans of bailed-out lenders during the economic crash.
A criminal probe was launched after the publication of leaked messages between Mr Bryson, Mr McKay and the account of Mr O'Hara.
NAMA sold its 800 Northern Ireland linked properties to investment fund Cerberus for £1.2bn.
The Finance Committee inquiry was set up amid political controversy over the sale.
Mr Bryson has also written to former DUP minister and RHI whistleblower Jonathan Bell, who is known to have secretly taped conversations during his time at Stormont.
The loyalist is seeking any NAMA-related material that the former MLA may possess.
He is hoping to call former Alliance MLA Judith Cochrane, who served on the Finance Committee, as a defence witness.
The Alliance Party last night declined to comment.
DUP MLA Jim Wells has already agreed to be a defence witness.
The South Down representative, who served on the Finance Committee, has vowed to tell "nothing but the truth" at the trial.
He had the party whip withdrawn in 2018 after he criticised the DUP leadership.
In his 2015 evidence to the committee, Mr Bryson alleged that former DUP First Minister Peter Robinson was one of five people set to receive a payment after the NAMA deal.
Mr Robinson strenuously denied that he was a beneficiary and rejected the claims as "scurrilous and unfounded".
He branded Mr Bryson's evidence a "pantomime".
At the time of the hearing, Mr McKay was chair of the Finance Committee and seen as a rising star within Sinn Fein.
The following year, he was forced to resign as an MLA following the allegations that he and Mr O'Hara were involved in coaching Mr Bryson ahead of his committee appearance.
Police launched an investigation into the affair following a complaint from DUP chairman Lord Morrow. Mr Bryson is also seeking to call him as a witness.
There is no suggestion that those who Mr Bryson intends to call as witnesses are involved in the NAMA conspiracy issue.