Greggs expects up to a £15m loss for the year, which would be its first annual loss since it listed its shares on the stock exchange in 1984.

The bakery chain said it does not expect profits to return to pre-Covid levels until 2022 at the earliest.

It has been battling a sales slump due to the coronavirus pandemic, but sales declines have been lessening.

Greggs made 820 job cuts at the end of last year, after its sales were hit by coronavirus lockdowns and restrictions.

Chief executive Roger Whiteside said the impact of the Covid-19 crisis had been "enormous" and that a fresh lockdown meant "significant uncertainties remain in the near term".

Coronavirus restrictions towards the end of last year led to "variable trading conditions across the UK", he said.

Sales in the final three months of the year fell by nearly a fifth, but this decline was less than its sales slump in the third quarter.

In September, Greggs, which is based in Newcastle, said it was in talks with staff to cut hours in an effort to minimise job losses.

But it still decided to cut 820 jobs because of "lockdown levels of business" as High Streets were hit by the crisis.

"Looking ahead, the significant uncertainty over the duration of social restrictions, along with the impact of higher unemployment levels, makes it difficult to predict performance," the firm said.

"However, we do not expect that profits will return to pre-Covid levels until 2022 at the earliest."

Greggs said on Wednesday that total sales for the year were down nearly a third to £811m, but government support had helped to limit pre-tax losses.

It said it had developed its takeaway business and a delivery tie-up with Just Eat, and had also seen "strong sales" through its partnership with retailer Iceland.

"We have taken action to position Greggs to withstand further short-term shocks and are optimistic about our prospects for growth once social restrictions are lifted," Mr Whiteside added.

Greggs wants to open about 100 new stores, on a net basis, over the year ahead.

Julie Palmer, a partner at insolvency consultants Begbies Traynor, said: "The latest national lockdown will be unwelcome news for Greggs, which has operated shrewdly during the past year in spite of a lack of footfall, with non-essential stores forced to close and millions working from home.

"The bakery chain has had to adapt its business model and invest digitally to accommodate for the rapid change in shopping habits, offering click-and-collect purchases, as well as a nationwide delivery service through its partnership with Just Eat.

"This should provide a solid base for the business to expand when government restrictions are eased and the world returns to some normality."