The national postal strikes in the UK have had a dramatic impact on e-commerce sales, according to the latest e-retail sales index from IMRG and Capgemini.

The figures reveal that growth in online spending fell by seven per cent over the two weeks of industrial action, and that sales declined by £53m.

Sales are still up year on year, and IMRG reported that British shoppers spent some £4.2bn online in October.

Concerns about delivery hit clothing sites particularly hard, as shoppers chose to return to the high street. Online clothing sales grew by just 13.2 per cent in October, compared to 27 per cent a year ago.

"While the overall Index returned to double-digit growth in October, the decline in e-retail sales values and volumes during the second half of the month shows that consumer confidence was affected by the Royal Mail strikes," said Tina Spooner, director of information at the IMRG.

"However, with the threat of further strike action now averted in the run up to Christmas, concerns around delivery will no doubt be dissipated."

The report showed that Christmas shoppers have not shied away from buying gifts, spending 113 per cent more in October than in September and an impressive 40 per cent more than in October 2008.

"E-retailers must heed the October warning signs and act to reassure consumers that orders will be delivered in time for Christmas," said Mike Petevinos, head of retail consulting at Capgemini UK.

"With consumer confidence restored, e-retailers can get on with the real challenge of convincing consumers to spend online and resist the temptation to wait even longer for last minute discounting on the high street. Ironically, careful tactical online promotions may be the route many adopt."