The Union of Communication Workers staged a 24-hour strike in protest at the closure of Crown offices and the transfer of businesses to franchises often in supermarkets. The union claimed 3,400 of its members were on strike, although management put the figure at 1,600.
It also claimed that a leaked document showed that the privately-run offices were less efficient than those staffed by post office employees.
An internal document covereing south-east London showed that cash accounting mistakes at the franchised office in Blackheath were 78 per cent above the post office's own target from April to July this year. In the same period crown offices in the locality registered no cash errors.
The error report, issued from the post office's main accounts office in Chesterfield, Derbyshire, and leaked to the UCW, showed that mistakes in handling Girobank transactions ran at almost three times the target rate and six times more than the nearest crown post office.
Alan Johnson, general secretary of the union, said it was "ridiculous" for the Government to claim that the service was improved by allowing supermarkets to take over the operation.
However, a management spokesman said the policy to offer franchises was a success for customers, retailers and the post office business. He added: "It is clear that the service has pulling power because retailers' turnover invariably increases when a post office service is provided.''
He said the cash discrepancies were "negligible" when compared with the full range of services provided by the franchisees and their longer working hours. "In most cases it is no more than a few pounds.''
Management said yesterday that nationally 647 out of 764 Crown offices remained open yesterday and the action was therefore "a flop". The corporation claimed the disruption affected less than half a per cent of the country's 20,000 post offices, pointin
g out that the dispute involved counter clerks only and did not affect Royal Mail and Parcelforce staff.
The union said that not all offices had been called out and that 95 per cent of its members in areas concerned had stayed away from work.