Strathclyde University's Professor of Politics, John Curtice, has said the Conservatives can no longer win a majority.
Speaking on the BBC, Curtice said it looks as though "our forecast is going to prove remarkably accurate, maybe in the end, the most accurate exit poll yet".
He said there was "no doubt" a hung parliament was on the agenda, adding: "We cannot see any way at all that the Conservatives can get to the 326 mark, and we think it's pretty clear that there is going to be a hung parliament".
Curtice said questions over the Prime Minister's future are set to become increasingly important later in the day.
The Prime Minister has already faced calls to resign, with opposition leader Jeremy Corbyn leading the charge.
Corbyn said the PM should "make way for a government that is truly representative of this country". May has retained her seat in Maidenhead.
Reflecting on results across the country, he said: "Politics has changed, and politics isn’t going back into the box where it was before".
Corbyn added: "People have said they have had quite enough of austerity politics. They've had quite enough of cuts in public expenditure."
Former Conservative business minister and Tory rebel Anna Soubry also launched an attack on her party leader Theresa May, saying the Prime Minister must consider her position.
Results suggest the Conservatives have had a disappointing night with the UK set for a hung parliament.