Waitrose this morning claimed that Marks & Spencer’s high-profile price comparison ad campaign has helped its own sales.

This month, M&S began running ads featuring the strapline ” strapline “Price checked against Waitrose Essentials. Quality checked by M&S”.

The John Lewis Partnership-owned grocer said that Essential Watirose lines featured in the ads soared, with tea bags up 96% and penne, sausages, spaghetti and teacakes all up by over 40%.

“Maybe we should be thanking the M&S marketing department for highlighting the quality and value of our range,” said commercial director Richard Hodgson.

Overall in the seven days to 7 November Waitrose enjoyed its highest sales growth in a normal trading week since 2006, with sales up 17.1%. Online business WaitroseDeliver showed sales up 86% year on year, helped by the abolition of delivery charges.

Sister department store chain John Lewis also had a very strong week, with sales up 13.2%. There was double digit sales growth on six of the seven days and all but one store recorded a sales increase.

Electricals and home technology was up over 20%, while furniture had a stunning week, up 33% with beds leading the way. Toys are enjoying a strong build-up to Christmas - particularly “anything animal related” according to director of selling operations Nat Wakely.