Plans to sell off part of Royal Mail were opposed by many Labour MPs
Labour delegates have backed calls for the government to take responsibility for Royal Mail's pension deficit.
The government had planned to take the £8bn deficit on, as part of plans to part-privatise Royal Mail, which were shelved in July.
In an emergency resolution at the party conference, the government was urged to "resolve this matter immediately".
However the debate - used by unions and local parties to make a point - has no formal role in party policy.
The emergency resolution stated that Royal Mail chief executive Adam Crozier had said the deficit might have reached £10bn and said it was "vital to achieve an early end to this destabilisation of the industry which can only alarm postal worker and customers of the service".
It called on the government "as sole shareholder, to take on its responsibility for the deficit and engage with all the stakeholders to resolve this matter immediately following conference".
The motion was put forward by the Communication Workers Union which has been holding strikes across the country in a bitter row over jobs, pay and services. It was seconded by Unite.
The controversial plans to part privatise Royal Mail were put on hold after a backlash from more than 140 Labour MPs.