Michael Lever, who has spent 20 years as a banking analyst, started at the agency this month.
Before Credit Suisse, Lever worked at HSBC Securities as a banking analyst and spent nine years at the Bank of England. He has often been quoted in national newspapers giving advice on City stories.
'He has covered and had contact with every major bank during his career,' said Brunswick senior partner Susan Gilchrist.
'He will be able to give immediate senior insight to retained clients such as Barclays.'
Long-term client Barclays is currently looking at fund-raising schemes to boost its coffers as it feels the effect of the global credit crunch.
Brunswick is also advising Alliance & Leicester on one of the year's biggest banking deals, as it completes a £1.3bn takeover from Spanish firm Santander (PRWeek, 18 July).
Santander used Brunswick when it approached Abbey four years ago. Alliance & Leicester was a retained client before the deal took place.