The Democratic Unionists are standing by Health Minister Jim Wells amid mounting calls for him to resign over controversial remarks about gay marriage and child abuse.

Sinn Fein Deputy First Minister Martin McGuinness insisted Mr Wells' position as a Stormont minister is not tenable after he suggested a child was at more risk of abuse if brought up in a homosexual relationship.

Liberal Democrat leader Nick Clegg said the furore was an indication of the "truly backward-looking views from the DUP", but he would not rule out governing alongside the party after the general election.

The nationalist SDLP are to table a motion of no confidence in the minister at Stormont.

Police are also investigating a complaint lodged about the comments made by the South Down MLA at an election husting event in County Down on Thursday for which Mr Wells apologised.

The DUP's stance on LGBT issues, such as its opposition to gay marriage, has been subject to greater scrutiny due to the party's possible key role in a possible coaltion.

"Jim Wells' attack on the LGBT community was reprehensible and completely unacceptable from someone holding the position of health minister," said Mr McGuinness.

However, the Sinn Fein veteran claimed the apology "rang hollow."

DUP leader Peter Robinson pointed out Mr Wells' wife has been ill: "Anybody who looks at the comments will recognise that on a better day Jim would never have made such a comment. He has put out a very sincere and fulsome apology and I think people should give him a break."