British Airways is set to be fined more than £183 million over a customer data breach, the airline has announced.

Alex Cruz, British Airways chairman and chief executive, said he was “surprised and disappointed” by the proposal from the Information Commissioner’s Office (ICO).

Willie Walsh, boss of the British Airways’ parent company International Airlines Group, pledged to “defend the airline’s position vigorously, including making any necessary appeals”.

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The ICO has indicated that it plans to impose a penalty of £183.4 million, which represents 1.5% of the airline’s annual turnover.

Details of the data breach were made public on September 6 and October 25 last year.

It relates to the theft of customers’ personal and financial information between August 21 2018 and September 5 2018 from the website ba.com and the airline’s mobile app.

The airline initially said around 380,000 payment cards had been compromised.