The Royal Mail missed its quality of service targets at the end of last year after deliveries were disrupted by a series of strikes, it was announced yesterday.

In the three months to December, 78.8 per cent of first class post arrived the next day, against a target of 93 per cent, while 93.3 per cent of second class letters were delivered within three working days, below the 98.5 per cent target. Business bulk mail services were also below target in the autumn quarter, although targets for European international delivery mail were exceeded by 7.5 per cent.

Mark Higson, managing director of Royal Mail Letters, said: "We are clearly concerned that customer service was disrupted by industrial action, but strike action ended with the interim agreement reached with the union in early November and we are now completely focused on restoring quality of service to the record above target level we achieved in the Spring of 2009, prior to the strikes."

The Communication Workers Union held a series of nationwide strikes last autumn in a row over jobs and working practices and has been holding talks for several weeks with the company to try to reach an agreement to resolve the dispute.

Nigel Woods, of Consumer Focus, said: "Whether or not these results are down to industrial action, consumers were let down by Royal Mail last autumn.

"The figures are similar to those recorded during the industrial action of 2007-8 and show how important it is for Royal Mail to resolve their industrial relations problems once and for all.