DUP MP Ian Paisley Jr prompted laughter in the Commons on Tuesday when he said allowing gay people to get married would cause fewer heterosexual people to wed.
Speaking during the debate on the coalition's same-sex marriage Bill this afternoon, the North Antrim MP who opposes the legislation, pointed to the experience of other European countries.
"Since same-sex marriages were introduced in Portugal, Spain and the Netherlands, mixed sex mariages have decreased quite considerably, indeed by tens and tens of thousands," he said. "The facts are clear."
However Yvette Cooper, the shadow minister for equalities, said she doubted there was a link between gay people getting married and straight people deciding not to.
"I can say if you looked at long term trends in marriage across a whole series of different countries, those that have same-sex marriage and those that don't, I think he would struggle to find a causal connection between the idea that some gay and lesbian couples are now able to get married has somehow meant the heterosexual couples are running away from the church door or registry office," she said.
A study by fact-checking website Full Fact showed that marriage rates in some European nations had declined since same-sex marriage was introduced - but this was a continuation of a trend.
The study also found that marriage rates in Belgium had actually increased since the introduction of same-sex marriage.
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