Keir Starmer stopped using a personal email account when he was opposition leader after being warned about a suspected hack by a Russian group, it has been reported.

The suspected breach happened in 2022, shortly after the Russian invasion of Ukraine, according to a book about the Labour leader, reported the Times.

According to the book, Get In, Starmer’s team first knew about the incident when Jill Cuthbertson, who heads his private office, sent round a message instructing other staff to no longer send messages to the email address.

This happened after staff from Starmer’s office were warned about the possible hack of the account by the National Cyber Security Centre. The warning said it was possible that sensitive information could have been taken, although none was published, the Times said.

According to the paper, the previous address had been “dangerously obvious” and lacked the backup security of two-factor authentication, under which an attempted login from an unknown device requires a separate identity check. These were both addressed for Starmer’s replacement account.

Around the same time as the suspected Starmer security breach, a collection of emails from Sir Richard Dearlove, a former director of MI6, and other figures was published after an apparent hack also by a Russian group.

At the time, Google said the release of the emails appeared to be the work of a Russian group it called Coldriver. The hackers published emails from Dearlove and others claiming they detailed the work of a group of pro-Brexit plotters.

Instead, the bulk of the emails, dating from 2018 to 2019, showed a selection of Brexit supporters frustrated with then-prime minister Theresa May’s willingness to seek compromises with the EU.