Mark Davies, the Communications Director for the Post Office, said: "We apologise to our customers who are being inconvenienced by the strikes today."
He added that the Post Office's transformation plan aimed to reduce the company's losses by investing in Crown offices.
The Post Office's transformation plan is based "overwhelmingly on cost-cutting", the Communication Workers Union said. It claimed:
- Plans rely on staff cost cutting to account for more than half of all cost reductions
- Only 20% of the gap to break-even will come from new income
- Reliance on franchising is up by £2 million to £8 million compared to last September
- The management's pay offer of lump sums is conditional on reaching "unrealistic savings through closure of offices", many staff are likely to never receive the money on offer it said
Workers at Crown Post Offices will stage a strike today, as part of a dispute over franchising, jobs and pay.
Members of the Communication Workers Union voted 88% in favour of strike action, on a 75% turnout on 8th March 2013.
Post Office staff have previously taken action on Easter Saturday, April 19 and April 29.
Read: Post Office workers go on strike around the UK
Four thousand Post Office workers will strike today in a dispute against plans to freeze wages and close 20% of the network.
It is the fourth time workers will stage a protest since Easter, today's strike involves staff working at more than 370 Crown offices, affecting 800 jobs.
The Communication Workers Union says staff have not had a pay rise since April 2011.
It believes the Post Office's 'transformation' plans are based overwhelmingly on cost-cutting.
Read: Crown Post Office workers to strike again
The Communication Workers Union says staff in hundreds of Crown Post Offices will stage a fresh strike on May 7 in a row over jobs, pay and branch closures.