Postal workers belonging to the Communication Workers Union walked out at noon (1100 GMT) after last-minute talks with management failed to resolve a long-running dispute. They plan another two-day strike starting Monday, leaving most Britons without mail delivery for almost a week.

Royal Mail employees have staged four national strikes and other forms of industrial action since the summer, when they rejected a 2.5 percent pay increase and the Royal Mail's modernization plans, which the union claims would cut 40,000 jobs.

The union said the employer was going ahead with changes to pensions, including increased employee contributions, a later retirement age and later starts to shifts.

Royal Mail says the modernization plans are vital to help secure a successful future for the company.