THOUSANDS of bank workers need reassurance about the future of Clydesdale Bank, their trade union said.

Unite was responding to the announcement that Clydesdale and Yorkshire banks will be put up for sale, possibly through a stock market flotation. Owner National Australia Bank (NAB) says its long-desired exit from the UK has become "more urgent".

Clydesdale employs 3,700 people in Scotland out of NAB's total 7,100 in the UK.

Alex Flynn, a Unite spokesman, said: "We are seeking clarity over the proposed sale of Clydesdale and Yorkshire banks, particularly on the timetable and the form that would take.

"Over the last 18 months 1,400 people have lost their jobs across these two brands and we have seen a number of branch closures. These people need certainty."

Mr Flynn said it was the banks' workforce which was behind the improvement in profits and performance disclosed by NAB, with cash earnings doubling last year to £158 million, and bad debts halving to £80m.

On job security, David Thorburn, the Clydesdale's Glasgow-based chief executive, said that while efficiency gains would continue he was "not announcing major restructuring today".

The bank announced the closure of 16 branches in April and Mr Thorburn said more closures were inevitable, adding: "We are doing a lot of research on how people want to interact with us and there is a strong migration towards digital and the internet."

NAB stressed its "disappointment" that its two UK banks had doubled their provisions for the mis-selling of payment protection insurance (PPI) and complex business loans to over £800m.

A year ago the bank was fined £8.9m and had to repay customers £42m, for mortgage calculation errors.

Mr Thorburn said another regulatory fine, for its PPI claims handling, was "a distinct possibility".

He added: "But I think it would be unfair to say we have behaved differently to other banks, all banks have had their problems."