The Government made a controversial move to end the postal dispute yesterday by pressing workers to accept an existing offer from Royal Mail.

The intervention from the Prime Minister and John Hutton, the Business Secretary, was made as new wildcat walkouts took place at mail centres across the country.

Gordon Brown and Mr Hutton called for the Communication Workers Union (CWU) to accept an offer on pay and pensions and to sort out differences over working arrangements with Royal Mail. The major dispute between the two sides concerns working flexibility, with Royal Mail demanding an end to what it calls Spanish practices. The TUC General Secretary, Brendan Barber, criticised the Government’s intervention, saying that it would not assist progress towards a resolution.

The Government’s calls for an end to the action came as the sixth national strike day ended in the early hours of yesterday, but wildcat action took place in London, Liverpool and Glas-gow. The unofficial walkouts, involving about 2,000 employees, were in protest at new starting times imposed by Royal Mail. The postal group moved the start times at some offices from 5am to 6am because it is phasing in slower-speed lorries in preparation for new legislation on driving speeds next January.

Gordon Brown said at Prime Minister’s Questions that there was no justification for carrying on the strike, which has paralysed postal services since last Thursday, and that the dispute should be “brought to an end on the terms that have been offered”. Mr Hutton said later that the Government was on the side of the taxpayers, who were the owners of the postal group.

He said that the offer of a 2.5 per cent pay rise was fair and that Royal Mail was at risk of “irreparable damage” if the strike action continued.

Mr Barber, who has chaired days of talks between the two sides, said: “I am disappointed that the Prime Minister should intervene in this way, at such a delicate stage in the negotiations. This will not help find a sustainable resolution to the dispute.” The CWU said: “The CWU believes the time is right for the Government to intervene in a positive way to resolve the dispute. Talks are due to resume today and the CWU remains committed to achieving an agreement.”

Royal Mail said that wildcat action had affected 24 of its operations, but that 98 per cent of its facilities were working normally. Work was focused yesterday on clearing the backlog of mail that had built up after two 48-hour strikes.

Two other national strikes were held in July while selective action took place across different parts of the network for three weeks, also in July.

Next week more selective walkouts are planned to run indefinitely until an agreement is reached. The action will start on Monday with a walkout at mail centres – the large post processing operations – and airport distribution centres.

Business and postal consumers’ groups have given warning that customers will desert Royal Mail permanently because of the uncertainty of its service. Parts of the mail order industry have been hit particularly hard.

Royal Mail says that it needs to tackle 92 restrictive Spanish practices, including leaving early when a job is finished, claiming two to three hours’ overtime if only 30 minutes of overtime is worked, and an absence of flexibility of work in the same office. It says that some delivery offices ask for overtime rates if a temporary person is brought in.

It conceded that Allan Leighton, its chairman, had guaranteed early finishing in the “job and finish” and that there were not 92 different types of restrictive practices but 92 examples of them being practised in different locations. Royal Mail said that none of the practices was endemic.

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