The Post Office said fewer customers and losses of almost £4m a week are behind the proposed closure of 22 of its Oxfordshire branches.
A list of the branches facing the axe was leaked on Friday ahead of an official announcement tomorrow.
The Government has said 2,500 branches must close by the end of the year.
Post Offices spokesman Jaquie Stenson said: "Post Offices play an important social and economic role in the communities they serve.
"But with new technology, changing lifestyles and a wider choice of ways of accessing services, people are visiting Post Offices less.
"The network's losses rose from about £2m a week in 2005 to almost £4m a week last year and are likely to increase further unless action is taken to make the network more sustainable.
"The present Post Office branch network is not sustainable and the Government has decided upon this controlled closure programme to ensure all our customers across the UK still have reasonably good access to Post Office services."
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