A report by top lawyer Anthony Salz, who was commissioned to look at the bank's culture following its £290 million Libor settlement last year, found Barclays became "too complex to manage" and that excessive pay and bonuses saw some bankers believe they were "unaffected by the rules".
In the 244-page report, which follows more than 600 interviews over eight months, Mr Salz calls for Barclays to bolster its board, strengthen its human resources function and ensure pay is linked to the "long-term success of the institution".
He said Barclays has already taken steps to revamp its pay policies and culture, but added that more needed to be done.
"If Barclays is to achieve a material improvement in its reputation, it will need to continue to make changes to its top levels of pay so as to reflect talent and contribution more realistically, and in ways that mean something to the general public," the report said.
Sir David Walker, chairman of Barclays, admitted the report made for "uncomfortable reading". He said: "That is bound to be the case when one asks for an independent examination of this kind, and we must learn from the findings."
The Salz Review revealed the bank's investment banking arm paid out an average of £170 million a year between 2002 and 2009 under its long-term incentive scheme - on top of salary and annual bonuses. It said there were "a number of design issues" with the long-term bonus plan, with targets that were too easy to achieve.
While Barclays has recently announced changes to its bonus plans, the review raised concerns that its long-term schemes were still too complex. It also said there were worries over bonuses for those in so-called control functions - such as risk management - and recommended increasing fixed pay instead to avoid conflicts of interest.
Barclays plans to report back on the Salz Review before its annual general meeting on April 25.