Tesco is back in the driving seat with aggressive promotions leading to a market share gain for the first time since May, while rival Morrisons’ share has slipped for the first time since 2007.

According to Kantar Worldpanel, for the 12 weeks ending November 28, Tesco increased its market share from 30.6% to 30.7%. Morrisons, which has been growing share for three years, saw its share slip from 12.1% to 12%.

Jefferies International analyst James Grzinic said Tesco has experienced “the most obvious improvement in trading momentum”, adding that Tesco’s Clubcard Voucher Exchange campaign will have helped grow sales.

Bernstein analyst Christopher Hogbin said Tesco has strongly outperformed. He added that Morrisons’ “significant slowdown” comes as the sales benefits enjoyed from the stores it bought from the Co-op last year come to an end.

Grzinic said Morrisons may have also suffered from rival Asda copying its Christmas voucher campaign this year.

Asda’s share has stabilised for the first time this year, at 17%, while the star performer in Kantar’s figures remains Sainsbury’s, which increased its share from 16.1% a year ago to 16.4%.