John Lewis , Britain's biggest department store chain, said on Thursday sales rose 20.7 percent year-on-year in the four days to December 21, albeit against a snow-hit period last year.

In-store sales have benefitted from the festive atmosphere created by partners (employees), while online sales soared in the run up to the cut off deadline for delivery yesterday, albeit when compared with snowy conditions last year, David Barford, director selling operations at the employee-owned group said.

The 20.7 percent figure is a gross number, inclusive of VAT sales tax and new space.

Analysts estimate the underlying figure to be about 13.7 percent, excluding VAT and new space.

On Sunday John Lewis reported gross sales for the week to December 17 up 10.6 percent to 133.1 million pounds, the highest weekly level in the company's history.

With Britons' disposable incomes being squeezed by rising prices, muted wages growth and government austerity measures, most retailers are nervous about spending in the key Christmas period and discounting is rife.

John Lewis has, however, been outperforming rivals for over a year. It will next update on trading on January 4.

(Reporting by James Davey; editing by Kate Holton)