Speaking to Sky News during Jeremy Hunt's Budget speech in the House of Commons, Mr Farage said NatWest's attempts to "cover… up" its reasons for closing his Coutts accounts last year had undermined investor and customer trust in it.

"For a retail NatWest share sale to work - as outlined by Jeremy Hunt in the Budget - investors must have confidence in the bank," he said.

"My debanking row with them is far from over.

"They dishonestly used a whitewash inquiry to deny the true reason for the bank giving me notice on my accounts.

"They acted in a politically prejudiced way against me and then deliberately tried to cover it up.

"Until they provide full disclosure and apologise for their behaviour, why should any retail customer trust them?"

NatWest share offering

In Wednesday's Budget, the chancellor said he had decided to pursue a multibillion pound retail offering of NatWest shares in the summer, subject to market conditions and value-for-money considerations.

The government continues to hold roughly 35% of NatWest, having steadily reduced its stake during the last eight years from - at one point - almost 85%.

Mr Farage has threatened to launch court proceedings against NatWest over the debanking row in a bid to obtain compensation for "reputational damage".

Dame Alison Rose, the bank's former boss, stepped down last year after it emerged that she had inaccurately briefed a BBC journalist about the closure of Mr Farage's accounts.

Thwaite appointment key

She has since been replaced by Paul Thwaite, whose move from interim to permanent boss of NatWest was confirmed last month.

Having a long-term boss in place is regarded as being essential to the success of a mass-market sale of NatWest's shares.

The size of the offering and of the discount that will be given to participating investors are among the details which have yet to be determined.

Sky News revealed earlier this year that ministers had drafted in M&C Saatchi, the advertising agency founded by the brothers who helped propel Margaret Thatcher to power, to orchestrate a campaign to persuade millions of Britons to buy NatWest shares.

NatWest, which changed its name from Royal Bank of Scotland Group in an attempt to shed the legacy of its hubristic overexpansion, was rescued from outright collapse by an emergency bailout that Fred Goodwin, its then boss, likened to "a drive-by shooting".