Ecclesiastical is to close its offices in Harrogate, Edinburgh, Belfast, Bristol and Cardiff. The move will result in the loss of more than 40 full-time jobs.
The restructuring will see expansion in its Manchester, Birmingham, Eastbourne and Cambridge offices.
The insurer's London office will be unaffected.
Intermediary operations manager Joe Gray said the improvement of service standards is one of the main reasons for the shake-up.
"We're aiming to improve our service levels which have suffered recently because we've been re-underwriting our book and transforming our business on to a new IT platform," he said.
The insurer will retain development underwriters in Cardiff, Belfast and either Edinburgh or Glasgow.
"Most brokers demand upfront contact with decision makers," Gray said.
The job losses will largely affect back-office support staff.