Postal workers have pledged to step up opposition to Royal Mail privatisation, warning that the sell-off would be a "disaster" for the industry.
The Communication Workers Union called on Labour to make it clear that the party will renationalise the postal group if it wins the next general election.
Delegates at the union's annual conference in Bournemouth expressed their "total opposition" to the Government's plans to privatise the Royal Mail and set out plans to "reinvigorate" their campaign.
General secretary Billy Hayes said the union was sending a strong message to firms "circling" the Royal Mail by making it clear that privatisation was not necessary.
"Privatisation would be a disaster for this industry, and while there is life in this union we will continue campaigning to keep the post public."
Deputy leader Dave Ward said the Labour party should be put on the spot and pledge to renationalise any parts of the Royal Mail which are sold off by the coalition, as well as reverse the "disastrous" police of liberalisation brought in by the previous Labour regime.
North East delegate John Woodhouse said: "There is no moral or economic case for privatising the Royal Mail. Post offices will be under threat, prices will go through the roof and the universal service will disappear into the sunset."
The conference agreed an emergency motion to continue campaigning against privatisation and to press Labour to repeal the postal service act which paved the way to the sell-off.
Royal Mail chief executive Moya Greene will address the CWU conference on Wednesday.