Northern Ireland Deputy First Minister Martin McGuinness has said an all-island investigation into the sale by NAMA of its Northern Irish loans should begin as soon as possible.

Mr McGuiness said the North's First Minister, Arlene Foster, had made it clear in Derry yesterday that the police investigations are important before other investigations go ahead.

He said Sinn Féin is clear that an all-island investigation should go ahead and said police investigations need to be expedited.

Mr McGuinness was speaking at the start of the second day of a gathering of Sinn Féin elected representatives from both sides of the border and the European Parliament.

Yesterday, an agreement was reached between the Government and Opposition parties that there should be a statutory investigation into NAMA arising from the Comptroller & Auditor General's report.

The report found that the agency incurred a potential loss to the taxpayer of £190m on the sale of its Northern Ireland portfolio after previous write downs were included.

Following its publication, the Cabinet agreed that there needs to be further investigation of the sale. 

This afternoon, Ms Foster repeated that it was her priority to await the work of the National Crime Agency inquiry and then review the situation.

She said she is aware of the Taoiseach's view about a new investigation but she has not yet discussed this matter with him.

In relation to Sinn Féin President Gerry Adams comments yesterday about stepping down in the future, Mr McGuinness said he and Mr Adams had a view about how it should be done.

He said it had to be endorsed by the party's Ard Comhairle.

Sinn Féin, meanwhile, will be appealing to EU leaders not to abandon Northern Ireland in the negotiations on Brexit, he said.

Mr McGuinness said British Prime Minister Theresa May could say what she liked about "Brexit meaning Brexit", but he added that the British government "does not have a clue about what that would look like in practice".

He said the British government had no plan to steer a course through, what he said was, the disaster they had created.

Mr McGuinness added that the British prime minister could not give any guarantees about an open Irish border, free trade or replacing EU funding as it will be subject to negotiations with other EU states.

The party'’s position was that the only way to guarantee a free border and other issues is through the North staying in the EU, he said.

He also said the actions of former Sinn Féin MLA Daithí McKay were wrong and the party had to move on.

Mr McKay resigned as MLA for North Antrim in August and was suspended from the party amid political controversy over allegations of coaching a witness during a Stormont committee hearing.

Elsewhere, Fianna Fáil leader Micheál Martin has said that the NAMA inquiry should start very quickly and a chairperson appointed, adding that work should begin immediately on drawing up the terms of reference. 

Speaking on RTÉ's News at One, Mr Martin said: "The immediate issue to be investigated is the Project Eagle sale.

"I think we need to move, albeit, conscious of the limitations that will face such a commission of investigation, but nonetheless I am satisfied that very useful work can be done now that the CAG report has been published."