Around 500 Communication Workers Union (CWU) representatives yesterday voted unanimously to press ahead with a strike ballot of 115,000 Royal Mail workers, no later than next month, if "satisfactory agreements" are not reached.
CWU general secretary Dave Ward said the current situation could not go on.
The ballot will focus on a national 24-hour strike, but will also include a decision on whether to boycott post delivered by Royal Mail for rival companies such as UK Mail and TNT.
"Postal workers are being squeezed in their workplaces, facing an uncertain future and changes to their pensions," said Ward.
"There hasn't yet been a pay rise for staff this year despite healthy company profits of £403 million. But most importantly, we want protections for job security and terms and conditions and these are sadly lacking."
He cited a consultative ballot in June, which showed 99% of postal workers back the union's position on pay, 96% are opposed to privatisation and 92% are willing to take part in a boycott of competitors' mail and to withdraw cooperation on workplace changes.
Ward added: "We do not take the decision to hold a strike ballot lightly. However, we will stop at nothing to ensure the future of our members' jobs - and of the services they deliver - are protected."
Royal Mail responded that it was "disappointed" at the decision and that a ballot was "inappropriate". It said the business operated "in a very competitive market" and "customers can move their business very quickly."
If the ballot goes ahead it will include 115,000 postal workers in Royal Mail (excluding Parcelforce and the Post Office). It would be the first ballot in Royal Mail since September 2009.
