Greggs has revealed its Norwich bakery is to close as part of a major shake-up of its manufacturing and distribution structure, which is feared to have put hundreds of jobs at risk.

All 50 jobs at Norwich are expected to be lost as production is transferred to other parts of the business over the coming year.

News of the closure follows the announcement that Greggs will be converting its Birmingham bakery into a distribution centre and restructuring its sites in Treforest, Wales, and Cambuslang, near Glasgow.

The activity is the next phase of a five-year, £100m investment in supply chain announced in March last year. This has included the previously announced closure of bakeries in Twickenham, Edinburgh and Sleaford and the opening of a new distribution centre in Enfield last year.

Greggs is making the changes so that the business, which currently operates around 1,800 shops, has distribution and manufacturing capability to service more than 2,000 in future. It is creating ‘centres of excellence’ that will be focused on distribution and/or production of a specific type of product.

Improvements in manufacturing efficiency are expected to see bakery production roles hit harder by job losses than those in distribution.

Workers at Treforest have been told 90 to 120 jobs are to go in total over the next 12 months to two years, while all 50 jobs at Norwich are expected to be lost.

Union Usdaw said restructuring at the Clydesmill Bakery, Cambuslang, would put a further 100 jobs at risk as Greggs concentrates production on “centres of excellence”.

“Greggs’ bakery staff are very concerned about the future after this announcement,” said Usdaw national officer Dave Gill.

Last week Greggs announced a 7% increase in group sales in the year to 31 December 2016, which included its 13th consecutive quarter of like-for-like growth.