Don dear, you have got it all wrong, but please don't bother to apologise.
The 2010 Labour Party leadership election was triggered by a general election on May 6th which resulted in a hung parliament. On 10 May, Gordon Brown resigned as Leader of the Labour Party. The following day, he stepped down as Prime Minister.[1] The National Executive Committee decided the timetable for the election the result of which would be announced at the annual party conference.[2][3] On 25 September, Ed Miliband became the new Leader of the Labour Party.[4]

Not one party went in to the last general election with same-sex marriage or any suggestion of changing marriage on their manifesto.
It had been discussed at no party conference, and no consultations had ever taken place.