National Australia Bank boss Cameron Clyne will retire in August.

The bank has announced Clyne will be replaced as chief executive by Bank of New Zealand boss Andrew Thornburn from August 1.

Clyne said leading the bank had been the most rewarding role of his career, but the job had taken a personal toll and it was time to retire from executive life.

“I am leaving to spend some much-needed time with my young family,” he said.

“I am proud that I leave NAB as a strong, customer-focused bank.”

NAB chairman Michael Chaney praised Clyne’s contribution to the company.

“Cameron took over as CEO during the global financial crisis and developed an effective strategy to steer the bank through a challenging period during which it has undergone significant cultural and structural change,” Chaney said.

“He is highly regarded throughout the bank and externally, and we are sorry to see him leave at this time.”

Andrew Thornburn has headed BNZ, which is wholly owned by NAB, since 2008 and was previously NAB’s head of retail banking.

He has also previously had responsibility for the bank’s Asian and US operations.

Chaney said Thorburn had driven a significant improvement in BNZ’s performance during his time as chief executive.

“Andrew Thorburn has done a superb job leading Bank of New Zealand since 2008 where he continued to build the bank’s performance, increasing cash earnings by more than 40 per cent, improving market share on the back of strong customer satisfaction and developing a strong leadership culture,” he said.

“As a member of the group executive team, his energy, vision and ability to motivate employees have been obvious as has his business acumen.”