Diane Abbott is facing criticism for posting a "misleading" tweet, which has been shared widely across social media and even used in Labour-affiliated advertising.
The shadow home secretary compared the media coverage of ex-Labour MP Ian Austin saying he would vote for the Conservatives with the coverage of former Tory MP Ken Clarke when he spoke of being conflicted about voting for his old party in the election.
She tweeted: "Ian Austin, one year as a junior minister at DCLG, says he won't vote for Labour. Wall-to-wall coverage. Ken Clarke, nine years as secretary of state, including as chancellor, says he won't vote for the Conservatives. Silence. Balanced election coverage?"
According to independent fact-checking organisation Full Fact, Ms Abbott's tweet is incorrect and misleading.
"While it's true that the two sets of comments received different levels of media attention, Ms Abbott's phrasing doesn't portray them entirely accurately, overstating what Ken Clarke said and implying the two sets of comments to be more similar than they are," it said.
"Mr Austin didn't just say he personally wouldn't vote Labour this election… he explicitly called on Labour voters to vote for the Conservatives. Meanwhile Ken Clarke did not say he 'won't vote for the Conservatives'.
"He did say that it was a possibility that he would not, but that it would depend on the campaign the Conservative party ran, and that he did not expect them to run a campaign which would cost them his vote."
The Labour Party declined to comment and has not removed the post from any of its platforms.
The BBC has contacted Ms Abbott's team, but they have not respond to calls or emails.
Ms Abbott's twitter account has 290,000 followers and her tweet has, so far, received more than 17,500 retweets and 44,000 likes on Twitter.
Despite criticism of it by Full Fact, an image of the tweet was shared by the official Labour Party Instagram account. The account has 90,000 followers, and the post has so far attracted more than 6,200 likes and almost 300 comments.
It has also been shared on Facebook by Ms Abbott, as well as Labour supporting groups, receiving around 4,000 interactions.
The tweet is also being used as a paid-for advert on Facebook and Instagram, funded by a Labour-affiliated group called Labour Future.
The organisation says on its website it is a group at "the cutting edge of modern campaigning", and it is working with Labour to "add value" and help the party win the election.
Full Fact says Mr Clarke's comments appeared to come from a Channel 4 interview on 1 November when he said his voting Conservative next month was "not as certain as it has been in previous elections".
He suggested his support depended on what sort of campaign the party ran.
"If we really do make ourselves the Brexit Party under our brand, my loyalty is going to be strained absolutely," he said.
"I am not voting for some crazy right-wing nationalist organisation calling themselves a Conservative government - but that, I think, is laying it on a bit. I don't think that's where we'll wind up."
The former chancellor, who is standing down from Parliament after nearly 50 years, prefaced his statement by telling his interviewer: "I'm slightly teasing you and myself."