Barclays is cutting the size of its investment bank so it accounts for about 30 percent of group capital, from 50 percent previously, and wants to improve its profitability so it delivers return on equity of 12 percent.

"In terms of building that model, I would say we are probably between 50 percent and two-thirds of the way there. We have some further work to do this year in terms of positioning the front office, then there's work to streamline the middle and back offices," he told reporters at a press conference following second quarter results.

Jenkins said he expects most of the front office changes to take place this year, while the middle and back office changes will run into next year. It will also take time to run down legacy investment bank assets that have been put into a pool of non-core assets the bank no longer wants.

(Reporting by Steve Slater; Editing by Matt Scuffham)