The Labour Party's leadership suffered a fourth defeat as the conference neared its end, with a vote for a fair share of funding for council housing.
The motion was carried unanimously.
Delegates backed a motion to provide extra funds for local authorities to build more council homes.
The government opposes the idea and instead wants councils to be encouraged to transfer their housing stock to housing associations.
Dave Trafford, of the union Amicus, said the issue was a "core value".
Known as the "fourth option" the motion would ensure funds available for stock transfers were equally available for direct investment in council housing.
The vote came despite pleas from Local Government Minister David Miliband, who warned the economy could be at risk from such a move, which was also proposed at last year's conference.
Public borrowing was limited because the government could not take risks with the economy, he said.
"So the only way to meet the demands of the motion would be to rob Peter to pay Paul less for new build or fewer people helped. We just can't do that."
Moving the motion, which was agreed unanimously, Pat Callaghan (Holborn and St Pancras) said: "No one wants privatisation of council housing. They see it as a direct threat to their security."
She condemned current arrangements for council house funding as "unfair" and warned it was more expensive to set up private companies to manage housing stock.
Dave Trafford, of the union Amicus, said: "I thought these were the things we believed in. I thought these were among our core values."
Delegates have already voted to support a return to secondary industrial action, the restoration of the link between the state pension and earnings, and limiting the involvement of the private sector in the running of the health service.
However, the Labour Party is making clear none of the votes will change government policy.