UK’s largest bakery chain Greggs (LON:GRG) warned on outlook for the full-year, after sales in the first quarter were hit by adverse weather conditions and low footfall.

Shares plunged nearly 20 percent at market open, after the group said it was uncertain about reaching full year targets due to a slower pace of sales in the first 18 weeks of the year. Total sales to the 5th May 2018 grew by 4.7 percent, almost half the 7.4 percent growth seen in the same period a year ago.

The group attributed the fall to “weak customer footfall in retail locations, which has impacted demand for food-on-the-go”, which was “especially significant in the weeks of severe weather when many shops, including our own, could not be opened”.

Like-for-like sales in company-managed shops grew by 1.3 percent over the same period, also slower than the 3.5 percent growth seen last year.

However, the group said “good progress” had been made with investments in its supply chain.

Looking forward, Greggs said: “Taking into account trading conditions in the year to date, and our more cautious outlook, we currently believe that underlying profits for the year are likely to be at a similar level to last year.”

Shares in Greggs are currently trading down 18.71 percent at 1,030.00 (0827GMT).