Martin McGuinness has said there are "very serious questions" about how Peter Robinson acted in relation to the sale of Nama's northern loan portfolio.
The North's deputy first minister said he was "kept in the dark" about a meeting in March 2014 involving the first minister and former US vice president Dan Quayle, now a senior figure with US vulture fund Cerberus, which bought the portfolio for €1.6bn last year.
Also present at the meeting, which took place a month before Cerberus bought the Project Eagle loans, were the North's finance minister, Simon Hamilton, and Belfast solicitor Ian Coulter.
Mr McGuinness told the Northern Assembly's Committee on Finance and Personnel he was "gobsmacked" when he learned about the meeting afterwards.
He also claimed he was never consulted about an apparent memorandum of understanding between the office of the first minister and a rival bidder, Pimco.
Earlier this year, Nama chairman Frank Daly described the memorandum as "a debtors charter" which the agency "would never have countenanced".
Under questioning, Mr McGuinness insisted he had never received a copy of the memorandum.
The deputy first minister also said it was "totally, absolutely misleading" for Mr Robinson's Democratic Unionist Party to say he had been kept informed about a bid from Pimco. Although Mr Robinson had at some point told him of the bid, which was subsequently withdrawn, Mr McGuinness insisted he was not given the detail of what was involved.
Meanwhile, Taoiseach Enda Kenny told the Dáil yesterday that he could not recall receiving a letter from another bidder for the portfolio, Fortress Capital.
It is reported the letter was sent in February last year and expressed concerns related to the business practices of third parties in connection with the deal.
Mr Kenny said he would have to check whether or not he had received the correspondence.
Nama said no such concerns were passed to it either by Mr Kenny or Fortress.