The Post Office has been accused of delivering a "huge blow" to its network after announcing plans to seek partnerships with retail firms for 70 of its main high street branches.
The company said the move will help the offices remain in their current locations, pledging no compulsory redundancies. But the Communication Workers Union (CWU) described the decision as the "partial destruction" of the so-called Crown office network.
Staff were in "shock" at the move, which would have a big impact on the high streets of small towns, said the union. There are 373 Crown Post Offices, sited mainly in high streets or busy shopping centres.
The Post Office said they were losing £40 million a year, so it was seeking retail partners for 70 branches, enabling them to stay in their current locations.
A number of Crown offices have closed over the years and services transferred to WH Smith and Co-op stores. The Post Office said it was seeking to link up with national partners, or local, independent firms, adding that if it could not find a suitable deal, the Crown office will remain.<
The Post Office said in a statement: "We are currently undertaking the biggest business transformation programme in the history of the Post Office.
"Our investment will maintain the size of the network and modernise branches to meet customer needs. Crown branches are a fundamental part of our long-term growth strategy and need to be brought into profit, currently operating at a £40 million annual loss."
CWU general secretary Billy Hayes said the announcement was a "huge blow" to the Post Office network, saying: "Staff will be in shock at the scale of what will effectively be the closures of Crown post offices across the country. This move will have a huge impact on the high streets of small towns earmarked to lose their Crown post office."
Robert Hammond, of Consumer Focus, said: "The Post Office network must change if it is to be sustainable.
"These changes to Crown post offices are part of the biggest-ever programme of change to the network and consumers will want to see Post Office services that are high-quality and accessible, and offer the products and services they need. This is more important than the issue of who operates the post office itself."