Workers in hundreds of Crown Post Offices are set to stage their 12th round of industrial action since Easter.
Members of the Communication Workers Union in England, Wales, Northern Ireland and most of Scotland will walk out on Monday, followed by a strike in a handful of branches in Scotland on Tuesday.
Staff are also taking other forms of action including a sales ban on financial products and services.
The union is opposed to plans to franchise or close 75 Crown offices, the larger sites usually found on high streets.
Workers in hundreds of Crown post offices are to stage a fresh strike next Monday in a row over pay, jobs and closures, the Communication Workers Union announced today.
Communication Workers Union spokesperson Andy Furey said Post Office workers did not want to strike, but were determined to "secure a fair settlement." He said he was optimistic about agreement being reached.
Roger Gale from the Post Office said the Communication Workers Union were making "unrealistic" pay demands considering the fact that the company is losing £37 million a year.
The union was asking for a pay increase of three and a half percent last year, and three and a quarter percent this year, which Mr Gale said was "unaffordable."
The network and sales director at the Post Office has said he is "disappointed" after the Communication Workers Union said its members will launch a fresh wave of strikes from today. Kevin Gilliland added:
This action can only cause disruption to customers, cost our people money and place further pressure on the Crown network which is currently losing £37 million a year.
We must continue with our plans to turn around the Crown network to ensure we keep these branches on high streets and in city centres across the UK.
Crown post office workers are prepared to take prolonged industrial action to defend jobs and win a fair pay rise, the deputy general secretary of the Communications Workers Union said today.
Dave Ward added:
This is the first time we have announced two days of strikes at the same time and the first time we have announced back-to-back days of strike action.
This is a company which made £94 million profit last year and paid out £15.4 million in bonuses to senior managers.
It's a clear case of double standards and trampling those at the bottom for the benefit of those at the top.
Workers at Crown post offices will today launch a fresh wave of strikes in an escalating row over jobs, pay and closures.
The Communication Workers Union said its members will walk out in the latest industrial action linked to plans to franchise or close more than 70 Crown sites - the larger branches usually found on high streets.
A UK-wide stoppage will be held today, staff in Scotland will strike on Monday, and union members in England, Wales and Northern Ireland will stop work on Tuesday.
Staff in hundreds of Crown Post Offices will stage a fresh strike today in a long-running row over closures, pay and jobs.
Members of the Communication Workers Union will walk out for half a day from 12.30pm, the eighth round of industrial action since Easter.
The union is campaigning against plans to franchise or close 75 of the Crown offices - the larger branches usually sited in high streets - saying it will hit jobs, and adding that staff have not had a pay rise for more than two years.
CWU deputy general secretary Dave Ward said: "Post Office plans to close offices, cut jobs and reduce services cannot go on unchallenged. It's time that Government stood up for these highly-valued local services which their constituents are signing petitions for in their tens of thousands.
With the news that Post Office staff shared £15.4 million in bonuses, their plans to close offices, cut jobs and refuse to agree a pay rise for Crown office staff is unbelievable.
They're lavishing bonuses at the top while slashing jobs, services and pay for frontline staff. It's blatant fat-cat behaviour from management out of touch with their workforce.
Post Office staff, customers and communities are continuing to stand up for the local Crown post office services they value so highly. The support continues to be enormous. Bosses cannot keep their heads in the sand forever.
Workers in hundreds of Crown post offices will take fresh strike action today in a long-running row over branch closures, jobs and pay.
Members of the Communication Workers Union (CWU) at up to 371 of the offices will walk out for 24 hours -in the seventh round of industrial action since Easter.
The union said growing numbers of members of the public and shop owners were supporting its campaign to stop plans to franchise or close 74 of the Crown offices - the larger branches usually sited in high streets.
Officials have warned that jobs will be lost if the plans go ahead, adding that staff have not had a pay rise for more than two years.