Sants, who left the Financial Services Authority in June, had been scoping out new roles at both Barclays and Deloitte.
He will take up his new position on 21 January, having already secured FSA approval for his appointment.
The 56-year-old will also be responsible for the bank’s relationships with governments and regulators, reporting directly to chief executive Antony Jenkins. His newly-created role does not come with a seat on the board, though Sants will join the executive committee.
Sants joins Barclays as the bank tries to rebuild its reputation following the Libor-rigging scandal, which led to the resignation of chief executive Bob Diamond and chairman Marcus Agius over the summer.
One of his first tasks will be to help steer the firm through an ongoing Serious Fraud Office probe into Barclays’ payments to Qatar Holdings in 2008.
He is also likely to be involved in dealing with the continued reputational fallout from the Libor-fixing investigation, which saw Barclays fined £290m in July.
“Relationships with our regulators and governments around the world are obviously also of critical importance to us,” said Jenkins yesterday. “We must apply a renewed leadership focus on these to make them as constructive and productive as possible.”
Sants resigned from the FSA after five years in the top job, spurning a new role as head of the new financial watchdog, the Prudential Regulation Authority.
He started his career at London-based broker Phillips & Drew, and headed up divisions at UBS and Credit Suisse First Boston before turning his hand to regulation.
Industry insiders said his banking pedigree meant a move to Barclays was a more natural choice than taking a position with Deloitte, thought to be his only other firm job offer on the table.
“I left the FSA with the intention of finding a role which would allow me to put into practice the experience I have gained in both the public and private sector,” said Sants in a statement.