The marginal seats where postal vote delays might swing results

Rishi Sunak, the Prime Minister, said it was “right” for Royal Mail to investigate concerns after Kevin Hollinrake, the postal minister, criticised the body for not recruiting the “right number of people”.

Sir Keir Starmer, the Labour leader, said on Tuesday that the Government should “get on with the job” and tackle the problems, adding: “We’re running out of time. It’s not something you can do tomorrow.”

Surge in popularity

Postal voting in its current form was introduced in 2001 and has since surged in popularity, accounting for 21 per cent of ballots in 2019.

The number of people voting by post is expected to increase by more than one million this year, to an estimated 10 million. 

Despite the increase, a similar timescale has been used for administering postal votes this year as in 2019.

Voters were given just under three weeks to apply for a postal ballot, between the dissolution of Parliament on May 30 and the deadline for applications of June 19.