CLYDESDALE Bank's new chief executive David Duffy is to start work next Friday with his first major task to guide the business through its stock market flotation.

Mr Duffy has been released from Allied Irish Banks with immediate effect after the lender promoted Bernard Byrne, its head of retail and business banking, to chief executive.

Clydesdale announced Mr Duffy would be the successor to David Thorburn earlier this year. Debbie Crosbie has filled the chief executive post on an interim basis since Mr Thorburn left at the end of February.

She will now return to her original role of chief operating officer.

Clydesdale's owner National Australia Bank has committed to a London initial public offering this year as a way to smooth its exit from the UK.

Mr Duffy said: "I'm delighted to be joining Clydesdale and Yorkshire Banks at what is a pivotal point in the Banks' story.

"With our parent company having announced that it intends to pursue a demerger and IPO of our business by the end of this calendar year, I'm looking forward to leading the Banks through this exciting new phase in their development.

"I passionately believe in our strong future prospects as a standalone bank in the UK market and in the journey underway to build a better bank for customers. My key focus will be to further build on the strength of the business and ensure Clydesdale and Yorkshire Banks provide a very real challenge to the big UK banks as a distinctive customer champion."

The 53-year-old Mr Duffy has been chief executive of Allied Irish Banks since December 2011.

The London-born executive began his career with Craig Gardner in Dublin in 1984 having studied for a Master of the Arts then Bachelor of Business Studies at Trinity College Dublin.

In 1987 he joined Goldman Sachs holding senior positions in its European divisions.

In February 1998 he moved to ING Barings at its global head of human resources and later that year was promoted to global chief operating officer.

During 2000 he was appointed to run the ING wholesale franchises in the United States and Latin America then four years later became the head of the global wholesale banking network.

In 2006 Standard Bank plc hired Mr Duffy as its chief executive and the next year be went to be the head of its international bank. He was living in Singapore a head of strategic projects when he took the Allied Irish job.

Mr Duffy has received all the relevant regulatory consent to take up his Clydesdale role.

Bank executives in Ireland are subject to a government-imposed salary cap of €500,000. Mr Duffy's remuneration at Clydesdale has not yet been disclosed.

Clydesdale chairman, Jim Pettigrew said: "We're delighted to welcome David Duffy as CEO of Clydesdale Bank.

"A passionate customer champion, David's decision to join us is a true vote of confidence in Clydesdale and Yorkshire Banks, our people and our future opportunities as a strong stand-alone bank in the UK market."

NAB has long seen its UK operations as a drag on the profits of its main Australian and New Zealand franchises.

Along with a slower than anticipated UK economic recovery Clydesdale was fined £8.9m in 2013 for miscalculating mortgages and then in April this year was handed a £20.7m fine by the Financial Conduct Authority for the way it handled payment protection insurance complaints.

NAB has also previously taken an impaired UK commercial property portfolio onto its own balance sheet.

Regulators have already asked NAB to provide up to £1.7bn for Clydesdale to cover potential misconduct charges relating to PPI and various types of complex business loans.