The Communication Workers' Union, whose leaders yesterday met executives from Consignia - the newly named Post Office - to negotiate a return to work, estimated last night that up to 50,000 workers had joined the rolling unofficial stoppages, triggered by industrial action in Watford.
Mail centre and delivery office workers walked out in London, Liverpool, Cardiff, North Wales, Manchester, Preston, Teesside, Maidstone, Stockport and Chester, a spokeswoman for Consignia confirmed yesterday, in a dispute which could delay the delivery of election polling cards.
More than 10m letters have already been delayed by the strikes and post boxes have been sealed in the most seriously affected areas, such as the north-west, but Consignia insisted last night that contingency plans were in hand to ensure election mail is delivered.
The disruption comes at a potentially embarrassing time for the government, which is already working behind the scenes with the TUC to convince the Rail Maritime and Transport union to call off planned London Underground strikes over privatisation safety fears - in the run up to polling day.
The postal stoppages spread after managers tried to divert mail to Liverpool and other sorting centres from strikebound Watford, where CWU members have been staging official walkouts in protest against new shift patterns, designed to deal with the rapid growth of junk mail.
The union agreed to flexible working in return for higher basic pay last year, but striking London postal workers said yesterday they were not prepared to accept the imposition of a move from 5.25am to 4am shift starts, and working patterns which entrenched part-time working.
Postal workers' discontent - which has already lost the Post Office 62,000 days through industrial action in the past year - has been further inflamed by threats from the government-appointed postal regulator, Martin Stanley, to introduce "serious" private postal competition by the autumn.
Mr Stanley, chief executive of the Postal Services Commission, who has been given a free hand by ministers to break Consignia's postal monopoly, has dismissed the Royal Mail as "simply incapable of change" and told postal workers they will end up in the same position as redundant Longbridge car workers unless they "get their act together".
Private delivery companies - such as the US-owned parcels corporation UPS, which become a regular financial donor to the Labour party - are poised to take advantage of the expected deregulation of the postal market, without the obligation to provide a national service at a uniform price.
Anger within the CWU at what is seen as the government's encouragement of creeping postal privatisation is likely to be expressed at its annual conference in the week of the election, when delegates are due to debate whether the union should consider backing anti-Labour candidates in future.
'We have to make a stand'
A crowd of postal staff grew outside Mount Pleasant sorting office in east London last night as those arriving for the late shift joined their colleagues and refused to start work.
Many expressed a feeling of sadness that industrial action had been necessary, but some said the strike had been too long in coming.
"It should have been done long ago. I am not happy at all. I am losing money, but you have to back other people up. We as night workers are losing more than everyone else," Dave, 43, a processing worker, said.
The father of two, who has worked at the sorting office for 19 years, added: "We are fairly tolerant but we have to make a stand somewhere. We are sort of sad about it but it has to be done.
"We lose out and that is a concern, but you have to say you won't be pushed around. The way we have to work inside there is ridiculous. The changes they have made are no better than how things were before. They said we would go forwards but, actually, we have gone backwards. It's a bit like a Dickensian workhouse."
A postman, 32, who declined to be named, said: "This is the straw that broke the camel's back. It comes down to one question doesn't it? How many times are you going to get kicked by them? It's not the management here that's the problem, it's the people higher up."
