Figures suggest just 11.6 percent of the total turnout at the last London Mayoral election had turned up at polling stations by midday. The figure is far lower than had been expected by the Labour Party, driving concerns of a shock result.
It is unclear who a lower turnout would benefit, results therefore more difficult to predict.
A Labour campaign source said Sadiq Khan‘s Khan’s team were “concerned” by the numbers being reported and that “voter turnout is very low”.
Sharing his fears on social media, Mr Khan issued a late rallying cry for people to make their voice heard.
He said on Twitter: “LONDON: reports show that voter turnout is low across our city.
READ MORE: Sadiq Khan accused of failing as Londoners head to polls
“If you love London and what we stand for, please come out and vote for it.
“We had a Tory mayor just five years ago – if you don’t vote, they could win again.
“Already voted? Please retweet and ask friends to vote Labour.”
Mr Khan is fighting for a second term at the ballot box, with Conservative candidate Shaun Bailey challenging him for the position.
Rallying his own supporters, Mr Bailey tweeted earlier: “Polling stations are now open across London.
“It’s time to give London a fresh start.
READ MORE: Car boot used as polling station as church warden oversleeps
The lower turnout so far today could be down to a change in voting habits due to coronavirus.
This year there has been a big push for more people to make use of a postal vote, therefore avoiding polling stations.
In a normal election year, many people also vote first in the morning on their way to work.
But with so many voters working from home due to offices being shut, it could be more people are planning to head to polling stations in the evening.
Polls have been open since 7am and will shut at 10pm tonight.
The results of the London Mayoral election are not expected to be known until Saturday evening.
City Hall officials expect the first results to be announced at approximately 6pm.
The pandemic means vote counting is expected to be slower than usual due to the need to abide by social distancing guidelines.
