Conservative diehards have crushed a rebellion by modernisers in the Shadow Cabinet who wanted the party to drop its opposition to allowing unmarried couples to adopt children.
The decision risks exposing to the Tories to the charge that they are ignoring the warning from their chairman, Theresa May, who told the party conference in Bournemouth: "You know what some people call us – the nasty party."
At last week's private meeting of the Shadow Cabinet, modernisers warned that they risked looking as "nasty" as ever if they stuck with their policy that gay couples and unmarried heterosexual couples should be barred from adopting.
They were outgunned by the traditionalists, led by the shadow Deputy Prime Minister, David Davis, the shadow Chancellor Michael Howard, and Liam Fox, the shadow Health Secretary, in charge of Tory policy on adoption.
Mr Duncan Smith waited for the discussion to finish before ruling that it would be a mistake to alter party policy now.
He told his colleagues: "The government may not be able to get their Bill through. Let's focus on the government's problems, not ours."
The decision means that when the Government's Adoption and Children Bill returns to the Commons, the Conservative front bench will be under instructions from the whips to vote against extending the right to adopt.
This proposal was thrown out by the Lords earlier this month, making a constitutional stand-off between the two Houses almost inevitable.
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