The watchdog said a variety of information was "compromised" by poor security arrangements at the company, including log in, payment card, and travel booking details as well name and address information.

The watchdog said BA had co-operated with its investigation and made improvements to its security arrangements.

The penalty is divided up between the other European data authorities, while the money that comes to the ICO goes directly to the Treasury.

It is up to individuals to claim money from BA, which provided no information on whether any compensation had been paid.

BA has 28 days to appeal. Willie Walsh, chief executive of IAG, said British Airways would be making representations to the ICO.