Millions of expatriates will be given a “vote for life” in elections in a move that could strengthen the Conservative Party’s grip on power.

The Government is to announce on Friday that it will scrap the 15-year limit after which more than three million Britons living overseas lose their right to vote.

The change – which will be subject to a vote in both Houses of Parliament – will apply to future general elections and give expats the right to vote in the last constituency where they lived.

Giving the vote to expats is likely to provide a significant boost to the Conservatives as many of them are retired and more likely to vote Tory.