The chairman and chief executive of Equifax, Richard Smith, has stepped down from the credit reference agency, following the massive data breach that resulted in the data of 143 million US customers being exposed.

Mr Smith's departure comes hot on the heels of two other senior executives – the chief information officer and head of security – less than two weeks ago, and amid an internal investigation into the hack as legal claims against the agency mount.

As well as the 143 million US customers whose data was unlawfully accessed between mid-May and July, with details stolen including bank and social security numbers, birth dates and driver's licence numbers, up to 400,000 UK consumers were also affected by the attack.

Although Equifax's UK systems were not accessed in the breach, a file containing British consumers' data had been stored in the US between 2011 and 2016. However, Equifax has said the file did not contain any addresses, passwords or financial information.

For the "fewer than 400,000" UK consumers affected, Equifax said it would offer them a free identity protection service.