The Co-op has hailed its “best Christmas ever” after its core convenience business registered a spike in sales during the festive season.

The mutual said grocery like-for-likes increased 6.2% during the two weeks to January 1, driven by a 9% increase in sales of seasonal products to £61m.

According to a note to employees from group chief executive Steve Murrells, the Co-op sold more than 16 million mince pies and 500,000 litres of Prosecco ahead of Christmas Day.

However, he warned that 2018 would be a “challenging” year, despite the Co-op’s ongoing momentum.

The c-store specialist has revived its fortunes in the past two years after investing in improving its own-label proposition and revamping its stores.

It is also in the process of acquiring retailer and wholesaler Nisa in a £143m deal as it bids to bolster its convenience and supply credentials.

Murrells said in the memo: “Thanks so much for all your fantastic efforts which set us up really well for 2018.

“This year’s going to be an exciting one, but it’ll also be challenging as we continue to change and grow our businesses.”