Sinn Féin president Mr Gerry Adams has urged the British government not to be distracted from the search for a solution in the North by the fallout of the Northern Ireland Secretarty Mr Peter Mandelson's resignation.
Mr Adams said: "It is a matter of public record that Peter Mandelson and Sinn Féin were in disagreement over many issues. Notwithstanding that, I wish him well for the future.
"I hope that the British Government is not distracted by the fallout of the resignation."
Mr Adams said now was a defining period in the search for a sustainable process towards a democratic peace settlement in Ireland.
"It requires a strategic approach by London, and particularly a very focused commitment by the British Prime Minister himself," said Mr Adams.
Sinn Féin's Assembly member Mr Connor Murphy said: "There have been many occasions, such as the suspension of the institutions, his dealing with the Patten Report and the flags issue, when he has been an impediment to progress."
The Ulster Unionist Party leader Mr David Trimble thanked Mr Mandelson for the work he has done in the North over last year.
Mr Dermott Nesbitt, of the Ulster Unionist Party, said it was sad for Mr Mandelson personally but the political process would continue.
"We in the Ulster Unionist Party want to see stability and we will work with whoever is appointed to replace him.
"We must dedicate ourselves to seeing we get for the people of Northern Ireland what they want."
The leader of the Alliance Party Mr Sean Neeson paid tribute to Mr Mandelson and said his unfortunate departure would not make resolving the problems in the Northern Ireland peace process any easier.
Mr Neeson said: "It is very unfortunate that the Secretary of State has had to step aside at this very sensitive and critical stage of the political process.
"The current circumstances are difficult, and for a major change to occur will not make things easier.
"Peter Mandelson approached the process fairly and with an even hand."
Mr Peter Robinson the deputy leader of the Democratic Unionist Party said few tears would be shed in Northern Ireland following the departure of Mr Mandelson.
"His support for the Belfast Agreement and his refusal to recognise the fact that we speak for the majority of the unionist community characterised his time in office", said Mr Robinson.
"Few people will be shedding any tears for Peter Mandelson on his leaving Northern Ireland but we are mindful of the fact that whoever replaces him will be following the same policy and will be trying to placate republicans and nationalists at this time."