THE search to find a successor to Clydesdale Bank chief executive David Thorburn has started after he announced his intention to step down.

The bank's parent, National Australia Bank, is already understood to have hired headhunters Korn Ferry to look at internal and external candidates.

NAB confirmed that the process to identify the next Clydesdale chief executive was "well underway".

Mr Thorburn, a banking veteran, has been in charge of Clydesdale and sister bank Yorkshire for almost four years and will stay on until his successor is in place.

However he admitted a long-term intention to lead the bank through its next phase, which is likely to involve a stock market flotation and a move away from ownership by NAB, was too much of a commitment to make.

He said: "I'm proud of the work my team and I have undertaken during my tenure as CEO, and I leave knowing that Clydesdale and Yorkshire banks are in much better shape. "However, having been CEO for almost four years, I came to the view that it was in the best interests of the business for me to stand down at this time and allow an injection of new leadership to take place.

"I believe that the business requires a five year commitment from me, particularly as NAB looks at options to accelerate the exit from its UK banking business and I felt this was a significant undertaking."

Mr Thorburn started his career as a graduate trainee with Clydesdale in 1978 then spent almost a decade at TSB between 1984 and 1993. He returned to Clydesdale in 1993.

The chartered banker, who turns 57 this month, has been on the executive team at Clydesdale since 2002 when he was appointed as chief operating officer.

His time as chief executive, after replacing Lynne Peacock in 2011, was challenging and he oversaw a major restructuring of the UK business which resulted in more than 1,400 jobs being cut.

Alongside that he had to deal with the fall-out of major issues including payment protection insurance mis-selling and small businesses being mis-sold complex business loans.

Both those issues are ongoing and the hundreds of millions of pounds put aside for compensation has dragged on NAB's performance.

The appointment of Andrew Thorburn, no relation, as NAB chief executive last year resulted in a far greater focus on exiting its UK operations.

Clydesdale's chief operating officer Andrew Hooper retired in October last year which led to a number of senior hires and new roles. Among those were distribution director David Gillespie, previously at Royal Bank of Scotland, and former Deloitte partner Ian Smith who came in as chief financial officer.

It is not yet known if any NAB and Clydesdale staff are in the frame for the top job.

Andrew Thorburn said: "David has been extraordinarily dedicated to improving the performance of our UK operations, and our business as a result is now in much better shape.

"Since our announcement in October 2014 that we intend to examine a broader range of options to accelerate the exit from our UK banking business, David and I have been having ongoing discussions about the future.

"David's decision is understandable given what is now required. He has made an excellent contribution to the bank, and I wish him well, and am pleased he is staying on to ensure a smooth transition."

It is expected the flotation of Clydesdale will take place after the UK general election in May although NAB has yet to confirm its plans.