Former Conservative leader Iain Duncan Smith has come close to embarrassing the party’s attempts at modernisation after appearing to suggest that gay couples cannot bring up children.

Launching a report on the importance of marriage and family to society, Mr Duncan Smith said gay couples were “irrelevant” to the work.

He told the Sunday Telegraph: “When it comes to gay couples they don’t even register on the Richter scale of how to bring up kids.

“Men and women are the ones who have the children. Gay couples have nothing to do with this at all.”

Tory leader David Cameron has been trying to shed the party’s previously homophobic image, and these remarks are likely to foster further doubts from critics regarding how much the party has changed.

However, Mr Duncan Smith attempted to bring himself back into line by clarifying that he was not judging the way same sex couples raise children, but was stating that the amount of gay parents do not affect the statistics.

The report by the party’s Social Justice Policy Group claims that the “collapse of family” is a key factor in social problems such as children joining gangs.

Mr Cameron will promise tax breaks to encourage marriage and will vow to make polices ‘parent friendly.’

The Conservatives recently became the first political party to join gay charity Stonewall’s workplace equality scheme.