Dame Alison Rose, former head of NatWest, breached Nigel Farage’s privacy rights by sharing information about his banking arrangements, the UK’s privacy watchdog has ruled.

The bank’s first female CEO resigned in July after admitting she had briefed a BBC journalist who reported that the former UKIP leader no longer met the financial requirements for an account with Coutts, its private banking subsidiary.

Mr Farage lodged a complaint with the Information Commissioner’s Office (ICO) which has now ruled that her action had infringed his rights and was “unacceptable”.

However, given she had stepped down and her former employer is investigating the case, it will not take further action at this time.

The BBC later apologised for its story, saying its reporting had been incomplete.

A spokesperson for the ICO said it had upheld two parts of Mr Farage’s complaint.

“We found that an individual employed by NatWest shared information when they should not have done, and that by doing so they infringed the complainant’s data protection rights,” it said.

“We have been clear with the bank that these actions were unacceptable and should not happen again”, it said, adding that since Dame Alison resigned her post and the bank had commissioned its own investigation, it will not take any further regulatory action at this time.

A NatWest spokesperson said: “We fully co-operate with the ICO in its assessment of any customer complaint but it would not be appropriate for us to comment on this individual case.”

The NatWest board is currently considering whether Dame Alison will receive £2.4m of pay contractually due to her, plus bonuses that could run to more than £5m.

The banking group, which includes Royal Bank of Scotland, is due to report its third quarter results on Friday.