In a tweet that was hastily deleted, the former foreign secretary said on Thursday night: “I just voted Conservative in the local elections. Make sure you do too! You’ve got two hours left to get out and vote!”
The MP has a home in London, where no local elections were held this week. He represents the west London constituency of Uxbridge and West Ruislip after stepping down as the capital’s mayor in 2016.
However, he also has a second house in South Oxfordshire, where polls were taking place on Thursday and where Mr Johnson reportedly cast a ballot.
His tweet was deleted 30 seconds after it was posted on Twitter, according to the website Politwoops, which documents tweets deleted by MPs.
But the swift erasure was not enough for him to escape criticism and scorn when the post was highlighted by comedy writer James Felton.
Labour backbencher David Lammy said Mr Johnson’s tweet exposed him as a “compulsive liar”.
“You cannot trust a single word he says,” he added.
Neil Coyle, another Labour MP, tweeted: “Boris Johnson struggles to know what day it is, what town he is in and if he even qualifies for a vote it seems. Lies yesterday, lies today, lies tomorrow.”
Actor Sanjeev Bhaskar joked: “Have voted. Haven’t voted. It’s such a fine line innit.”
However, according Henry Zeffman, a political correspondent for The Times, Mr Johnson voted in South Oxforshire's local election.
The journalist suggested the MP had deleted his tweet "because as the MP for Uxbridge it's not great to admit that you spend lots of time not in Uxbridge".
Voters with two homes can be registered at both on the electoral register but should only vote in an area where they have a “considerable degree of permanence”, according to the Electoral Commission.
While Mr Johnson endured a rough night on social media, his party was also suffering in the local elections. The Conservatives lost more than 440 seats and 17 councils across the country.
Labour also suffered losses, with voters seen as punishing both parties over Brexit.
The Liberal Democrats gained more than 300 seats, while the Greens declared “the biggest election night in our history” after scooping 42 seats.
The Independent has contacted Mr Johnson for comment.
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