Sinn Fein's finance spokesman in the Republic Pearse Doherty has said Finance Minister Mairtin O Muilleoir will have to resign from the party if it is found he was involved in the Nama witness coaching controversy.
Mr O Muilleoir is under pressure to step aside for the duration of an investigation into claims Sinn Fein MLA Daithi McKay sought to interfere with witness testimony before a committee hearing on the sale of Nama's Project Eagle loan book.
Mr McKay resigned almost immediately after it emerged he had been sending messages, through a third party on Twitter, to loyalist blogger Jamie Bryson before his committee appearance. Mr O Muilleoir has denied any knowledge of the correspondence.
Speaking outside Leinster House in Dublin, Mr Doherty said O Muilleoir would "of course" have to resign if he is implicated in the scandal.
However, he said he would be "shocked" if it emerges that the minister is found to have been involved in the plot to allege that former First Minister Peter Robinson benefited from the Project Eagle sale.
"Mairtin O Muilleoir has made a very robust defence and welcomes any investigation into that because his opponents who are using this as a political football will have to come up with the hard evidence rather than innuendo," Mr Doherty said.
He also insisted Mr McKay acted alone in contacting Mr Bryson and said he had and the rest of his party had no knowledge of the correspondence.
"I am the finance spokesperson, but I would imagine if this was something known within Sinn Fein, I would know," he said.
"Daithi McKay acted alone. He has made that clear and he has suffered the consequences for that, and it was the wrong thing for him to do at that time, but he has done the right thing in stepping aside," he added.
Philip McGuigan replaced Mr McKay as an MLA for North Antrim after he quit.
Mr O Muilleoir has insisted he will not be leaving his post. "There is no basis for me to step aside and I have no absolutely intention of doing so," he said on Tuesday.
Deputy First Minister Martin McGuinness has made clear that he has total confidence in Mr O Muilleoir.
"Mairtin O Muilleoir enjoys my full support as Finance Minister and he will not be stepping aside on the basis of calls from opposition parties, much less calls from the DUP," he said.