An exit poll cited by the BBC suggests Theresa May will miss out on an overall majority.
The influential poll, carried out by Ipsos Mori, suggests the Tories will pick up 314 votes - 12 short of the figure they need for a majority.
This would also represent a fall of 17 seats on the number of seats May's predecessor David Cameron won two years ago.
The figures suggest Labour would pick up 266 votes, 34 up on the figure they gained under Ed Miliband in 2015.
The SNP would pick up 34 seats, a sharp drop on their 2015 figure, while the Lib Dems would claim only 14 seats, despite their prominent anti-Brexit campaign.
The Tories have already spoken out against the poll, saying it is not representative of the views they have received up and down the country.