Thousands of Post Office counter staff are to be balloted for strikes in a row over pay, threatening disruption before Easter.
The Communication Workers Union said 4,000 of its members will vote over the next few weeks on whether to launch a campaign of industrial action.
The union accused the Post Office of refusing to consider a pay rise or guarantee there will be no more closures among the so-called crown offices - the larger offices usually based on high streets.
CWU deputy general secretary Dave Ward said: "The Post Office's attitude is about driving a race to the bottom on terms and conditions for staff and further downsizing the post office network.
"The company has no vision, and worse still appears to have no desire, to give staff a fair and just pay settlement or to work towards a sustainable post office network. Their approach spells disaster for Post Office employees and will further wreck the services that communities rely on."