Dame Alison stepped down from her role as chief executive in July after admitting she had talked with a BBC reporter about the ex-UKIP leader's relationship with Coutts - a NatWest subsidiary.

The Information Commissioner's Office (ICO) said its comments last month - in which the regulator said a NatWest employee shared information when they should not have done, and there were two privacy breaches - wrongly gave the impression it investigated the actions of Dame Alison.

"We confirm that we did not investigate Ms Rose's actions, given that NatWest was the data controller under investigation," the ICO said on Monday.

Instead, solely NatWest's actions as a data controller were investigated, rather than Dame Alison, the statement said.

It added: "We apologise to Ms Rose for suggesting that we had made a finding that she breached the UK GDPR [general data protection regulation] in respect of Mr Farage when we had not investigated her.

"Our investigation did not find that Ms Rose breached data protection law and we regret that our statement gave the impression that she did."

In its ruling in October, the ICO said there were two privacy breaches involved in the disclosure to BBC News business editor Simon Jack.

This enabled him to report Mr Farage no longer met the financial criteria to hold an account with Coutts, which is part of the NatWest Group.

Also included in the apology was the lack of any comment from Dame Alison. She should have been approached for comment, the ICO said.

"We accept that it would have been appropriate in the specific circumstances for us to have given Ms Rose an opportunity to comment on any findings in relation to her role and regret not doing so."

Initially the ICO said her actions were "unacceptable" but no further regulatory action was needed as she already resigned and NatWest, which is 38.6% state-owned, was conducting its own investigation.

The bank is preparing to cancel millions of pounds in bonuses and share awards owed to Dame Alison following her departure.

Dame Alison was on a £2.4m salary before leaving NatWest and is eligible to be considered for a pro-rata portion of the £2.9m annual bonus and long-term share awards that made up the remainder of her total maximum pay package of £5.3m.

The NatWest-commissioned independent review into the closure of Mr Farage's Coutts account and Dame Alison's discussion of his banking with Mr Jack found "a number of shortcomings" in the closure process.

But law firm Travers Smith also found the closure of Mr Farage's account "was predominantly a commercial decision".

"Coutts considered its relationship with Mr Farage to be commercially unviable because it was significantly lossmaking."

In response, Mr Farage said: "Travers Smith has taken a very mealy-mouthed approach to this complex issue. The law firm argues that my political views 'not aligning with those of the bank' was not in itself a political decision. This is laughable."

"Worse still, Travers Smith did not find 'any evidence' that my 'pro-Brexit stance were factors in the exit decision'. The word Brexit appeared no less than 86 times in my subject access request."