Delaney Lund Knox Warren & Partners, which also handles the accounts for Bank of Scotland retail and Halifax retail, has worked with esure for the past 18 months.
Esure, which was launched by Peter Wood, who founded Direct Line insurance, is in the process of producing a television campaign featuring Michael Winner that is due to launch later this year.
"We are enormously proud of the work we have done for esure," Greg Delaney, the chairman at DLKW, said. "We have - from a standing start - helped to create one of the strongest and most distinctive brands in the sector."
DLKW launched its first campaign for esure in August last year.
The campaign was based on the idea that consumers resent the fact that careful and responsible people subsidise the insurance payments of those who make regular claims.
The animated television spots presented the brand as offering a fresh alternative to conventional insurance, using the strapline: "Don't get mad, get esure."