Last-minute talks were being held last night to avert the longest strike at Royal Mail for 11 years.

The stakes have been raised since the last national walkout in July because of the effect on postal votes if a general election is called.

Postal workers are due to walk out today at midday in a two-day strike. But a further two-day strike starting on Monday morning will mean that mail posted today will not be delivered until next Thursday.

Postwatch, the consumers’ group, said that normal service was unlikely to resume before October 15, when another programme of selective walkouts is scheduled to start for an indefinite period.

The dispute between the Communication Workers Union and Royal Mail is over pay and pensions.

Royal Mail has offered a 2.5 per cent pay increase and wants to close the final-salary pension scheme to all employees.

Its move on pensions also threatens to provoke strike action from its managers.

Royal Mail and the union have been attacked for not resolving the long-running dispute. Millie Banerjee, chair of Postwatch, said: “It is hugely disappointing to watch a great British institution tear itself apart.”

Guy Buswell, the chief executive of Business Post, one of Royal Mail’s biggest rivals, said: “The long-running nature of this dispute is extremely detrimental to the whole mail business.

"In short, we believe this action, if it continues, is in danger of damaging the future of the mail industry.”

Royal Mail’s main rivals have to use its network for the final-mile delivery, so they are also caught up in the strike.

The National Federation of Sub-Postmasters said that the dispute could weaken Royal Mail and the whole post office network.

The CWU has been pressing the Government to intervene.

Billy Hayes, the CWU general secretary, is believed to have raised the issue with Gordon Brown at the Labour party conference.

Prolonged industrial action by the 130,000 postal workers in the dispute would be damaging at the start of an election campaign, if one is called next week.

It would also have serious implications for postal voting. Royal Mail said the issue was hypothetical and refused to say if it had contingency plans.

Dave Ward, deputy general secretary of the CWU, said: “Strikes are a proportionate response to an employer that is completely out of control. Rather than running the business, Royal Mail’s actions demonstrate they are intent on destroying it.”

A spokesman for Royal Mail said: “We will do all we can to mitigate the impact of the strike action, but we would ask our customers to avoid posting mail during the strikes and if they do so, then to post any mail at post office branches, which will all be open for business as usual.”

Times Recommends

• Minister in talks with Saudis to protect creditors
• Premier Inn hits back in £29-a-room row
• Bankers hit back at 'populist' bonus supertax