Andrew Thorburn, the new chief executive of National Australia Bank, will say a market flotation is one option for disposing of Clydesdale and Yorkshire banks when he gives his first full-year results presentation in Melbourne tomorrow night.

Mr Thorburn, who took over on August 1, has already announced plans for an IPO to offload the group's US subsidiary Great Western Bank.

But the new boss may allude to the choppy markets which have seen the recent flotation plans by Virgin Money and Aldermore hit bumps. Both of those, unlike the NAB banks, have a UK-wide franchise. TSB shares, meanwhile, are down by 9 per cent on their June flotation price.

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Earlier this month NAB had to issue a profit warning, citing the need for Clydesdale and Yorkshire banks to increase provisions for customer mis-selling redress by 50 per cent to more than £1.2billion.

The banks added £345m of new provisions relating to payment protection insurance (PPI) and £80m for claims on complex business loans.

Mr Thorburn said the issue was being dealt with "transparently and quickly", allowing the group to focus on its core Australian and New Zealand franchises, which remained in good shape.

NAB said there was still "a wide range of uncertain factors relevant to determining the total costs associated with conduct-related matters, including any possible fines".

The Herald has highlighted how the bank may have underlying claims yet to emerge in both areas. Claims companies have said Clydesdale is the only bank to reject most PPI claims dating back more than six years on the basis that it has destroyed all records, despite evidence that it has copies on microfiche.

The Treasury Select Committee meanwhile has grilled chief executive David Thorburn, no relation to Andrew, over the exclusion of the bank's most widely-sold small business loans, proven to be linked to derivatives, from the regulatory review of derivative-linked loans.

The Bully Banks campaign group has said it believes the current £250m provision is "way too inadequate".

Daniel Hall, managing director at business banking claims firm All Square, commented: "Time will tell if this represents a genuine attempt by the banks to address their conduct risk exposures, or whether mis-selling actually threatens to morph into a considerably more substantial problem." Any buyer of the banks "would need to do its homework and be able to calculate what it is inheriting",

NAB began clearing the decks for a disposal in 2012 when it removed a £5.6billion commercial loan portfolio from the balance sheets of the UK banks and exited property lending. It recently sold a £625m chunk of the portfolio to private equity group Cerberus and said the outstanding loan book had been halved to £2.38bn.

The group,which employs 3700 in Scotland out of 7100 in the UK, expects full-year earnings to be around 14 per cent lower than anticipated, at around £2.8 billion.