Mr Booker is the former group managing director and chief executive of HSBC North America, a role he took up in August 2010.
He will take up both the chief executive and deputy chief executive role at the Co-operative Bank from 10 June. He will also be a Board member. His appointment is subject to regulatory approvals.
Mr Booker will replace Barry Tootell who quit the firm earlier this month after the Co-operative withdrew from the purchase of 632 Lloyds TSB branches. In the same week, the firm was also downgraded by ratings agency Moodys from C- to E+.
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Euan Sutherland, group chief executive of The Co-operative Group, said: "We are delighted that Niall is joining the Co-operative Group. With his strong background across the banking sector, covering both retail and corporate, he is the ideal person to lead the Co-operative Bank at this important time in its history. He clearly brings the strategic and operational skills that we need to help take the Bank to the next stage of its development."
Mr Booker said: "I am delighted to be joining The Co-operative Group under Euan's leadership at this strategically important time for both the Bank and the Group.
"There are no quick fixes here, but with the support of The Co-operative Group, our staff and our loyal customer base, I am confident we will be able to stabilise and develop the franchise."

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