Nama scandal: Sinn Féin's Daithí McKay resigns after 'coaching' claims
Daithí McKay has resigned as an MLA after claims he and another Sinn Féin member "coached" loyalist blogger Jamie Bryson as a witness to an inquiry.
The allegations followed leaked Twitter messages between Mr Bryson, Mr McKay and Sinn Féin member Thomas O'Hara.
They exchanged messages before Mr Bryson testified to a Stormont inquiry, chaired by Mr McKay, into the National Asset Management Agency (Nama).
Mr McKay said he accepted this was "inappropriate, ill-advised and wrong".
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The outgoing MLA for North Antrim also apologised for his actions.
Sinn Féin chief whip Carál Ní Chuilín said Mr McKay had "accepted that he made an error of judgement" and had been suspended from the party.
She added on Thursday night that her party would "welcome and co-operate fully with any inquiry".
"Sinn Féin will co-operate fully with any inquiry and I am totally confident that any examination of the facts will confirm that Sinn Féin had absolutely no knowledge of, or involvement in, these events," she added.
Analysis: BBC News NI Political Editor Mark Devenport
Last September, Jamie Bryson used a Stormont finance committee hearing to make explosive claims about the multi-million pounds Nama property deal.
His evidence included an allegation that the then First Minister Peter Robinson was set to profit from the sale.
Now it has emerged that Mr Bryson was in contact with Daithí McKay and another Sinn Féin member about how exactly he should make his claims.
The DUP believes the latest revelation shows there was a dirty tricks operation against Mr Robinson, who strenuously denied any wrongdoing.
Now Mr McKay, once considered a party high-flyer, has submitted his resignation.
'Squeeze your best points'
The Stormont Finance Committee inquiry was set up last year due to political controversy over the multi-million pound sale of Nama's Northern Ireland property portfolio.
It followed an allegation made in the Dáil (Irish parliament) that a politician or political party in Northern Ireland stood to profit from the loan sale.
Last September, Mr Bryson used a meeting of the committee to name former DUP leader Peter Robinson as the individual he referred to as "Person A" in relation to the scandal.
The then first minister of Northern Ireland strongly denied he had sought to benefit in any way from the multi-million pound property deal.
It is now claimed that Sinn Féin's Mr McKay and Mr O'Hara advised Mr Bryson about his evidence before the hearing.
Leaked social media messages obtained by the BBC's Nolan Show and The Irish News show that on 17 September 2015, Mr McKay sent a direct message to Mr Bryson, telling him to follow a Twitter account in the name of Thomas O'Hara, who is understood to be a fellow Sinn Féin member.
The following day, a direct Twitter message from Mr O'Hara to Mr Bryson said: "You may only get 10-15 seconds on this before Daithi as chair has to pull you on it so squeeze your best points on this into 1-2 lines and come straight to the point."
Another message from him said: "Keep it short if you can, when it's said it's said and its privileged. Will be a great finisher."
In his resignation statement, Mr McKay said: "I want to be absolutely clear that my intention was not, as alleged, to coach the witness in question with regard to the substance of his testimony, but rather ensure that the inquiry had full access to the truth with regard to all the issues relating to the Nama scandal."
Shortly before Mr McKay's resignation on Thursday, Deputy First Minister Martin McGuinness vehemently denied having any knowledge about the exchange.
"Having spoken to all relevant personnel in the Assembly I am now entirely satisfied that Sinn Féin had no knowledge of any such contact."
But Ulster Unionist leader Mike Nesbitt said Mr McGuinness's statement "lacked the ring of truth" and was not the end of the matter.
The Alliance Party's deputy leader Naomi Long said: "This is something that an independent person is going to have to look into to restore some sort of public confidence."
SDLP leader Colum Eastwood said the "seriousness" of the claims "cannot and must not be underplayed".
Mr Bryson told the BBC that allegations he had been coached by Sinn Féin before giving evidence were "absolute nonsense".
"I can categorically state that the source of my information did not come from Sinn Féin," the blogger said.
He also denied leaking the information to the media.