Crown post office workers will be holding a one-day strike on Monday to protest at the franchising of branches.

Workers at the crown post offices those managed directly by Post Office Ltd in High Street, Barnet; Finchley Road, Golders Green; The Broadway, Mill Hill; Burnt Oak Broadway, Burnt Oak; and Darkes Lane, Potters Bar, will be taking part. The strike has been called by the Communication Workers' Union (CWU) London north-western counter and clerical branch.

A rally has been planned for 10am outside the Mill Hill office, with a public meeting to be held in Hartley Hall, Flower Lane, Mill Hill, at 1pm.

CWU branch secretary John Gaby apologised to customers for any inconvenience caused but said: "It is ironic that the one day we want to protest against the closures is the one day that Post Office Ltd is willing to keep them open. The rest of the year they are closing them down."

Melanie Corfield, head of external relations for the Post Office, said the company was putting in contingency arrangements for its customers. "We hope that we can keep all post offices open, and we are fairly confident that we will," she said.

Andrew Dismore, the Hendon MP, led a residents' protest at Post Office headquarters in Old Street, London, last Friday, where they met with Ms Corfield and Ian Anderson, the Post Office's human resources director, ahead of Mill Hill's handover to new owners, Supertex Ltd, on February 27. "We have seen no case for the justification of the franchise of Mill Hill post office and we are not going to go away," said to them. "We would ask you to change your decision."

The crown post office in Brent Street, Hendon, was taken over by M Hirsani Ltd on Monday.

To find out more about the crown post office contingency arrangements, call the Post Office's customer relations team on 08457 223344.