Sir Keir Starmer will hand the vote to millions of EU citizens if Labour wins the next general election, the Telegraph can reveal.
Under manifesto plans for the biggest expansion of the franchise in almost a century, Sir Keir will launch a “package of proposals” including votes for settled migrants and 16 and 17-year-olds.
The move could force the Conservatives out of London altogether and unseat Boris Johnson if he stands again for Parliament in 2029.
However, the Labour leader faces accusations of trying to “rig the outcome” of a future election and “laying the groundwork for a referendum to rejoin the EU”.
Under the proposals, migrants who live permanently in the UK and pay tax will be able to vote in general elections for the first time.
It is expected to affect around 3.4 million EU nationals in Britain, who have already fulfilled those requirements to achieve “settled status”. A further 2.6 million have already been granted “pre-settled” status and could be given voting rights in the future.
Labour would also expand the franchise to include 1.4 million 16 and 17-year-olds, increasing the size of the electorate by more than eight per cent in total.
Prof Sir John Curtice, the polling expert, said that migrants and young people were more likely to be Labour supporters.
Home Office data show migrants with settled status are heavily concentrated in large cities and the south of England.
“The presumption we all have, rightly or wrongly, is that they’re more likely to be opposed to Brexit, and therefore less likely to vote for the Conservative Party,” he said.
“London is already so overwhelmingly Labour – there are some Tory constituencies left, but not that many of them, and they are the ones that will be particularly on the line.”
He added that the policy “might help contribute to the downfall of Boris” in his west London constituency, which has a large migrant population, if he is still an MP after the next election.
An analysis by the Telegraph suggests senior Conservative MPs who may also be under threat include Bob Blackman, the executive secretary of the 1922 Committee, and Sir Iain Duncan Smith, the former party leader.
Labour’s plans to expand Britain’s electorate are expected to be announced in the party’s next manifesto, with detail being finalised among senior aides in the coming months.
Sir Keir called for “full voting rights for EU nationals” during his 2020 leadership campaign but there has been no policy announcement since then.
His other Brexit pledge to “defend free movement as we leave the EU” has since been abandoned, while the plan to introduce votes at 16 has been carried over from Jeremy Corbyn’s manifesto.
He doesn’t trust the British people’
A Labour spokesman said: “Keir fundamentally believes that if you work hard and contribute to this country, not only should you be able to get on, but it is fair and right that you should also have a say in decisions being made for your community.”