More than a million voters in the General Election may have been influenced by the BBC’s Question Time leaders special from York, according to new research.

The programme saw Theresa May and Jeremy Corbyn face an audience at the University of York days before the country went to the polls.

Now a study for the Electoral Reform Society found the debate swung a third of viewers’ votes.

Researchers found that 34% of the 2,500 people who were polled before and after they watched the programme said the show helped them make up their mind on who to back.

The total audience for the special was over four million viewers.

Jezza won it

Jeremy Corbyn on the TV screens in the University of York spin room. Photograph: YorkMix

Mr Corbyn gave the best performance, found research by Leeds University, with the strongest swing to the Labour leader among younger viewers – many of whom were undecided before tuning in.

The research also saw a surge in youth engagement in politics, with 80% of 18-24 year olds saying they were interested, compared to 50% in 2015.

Darren Hughes, chief executive of the Electoral Reform Society, said the study showed the importance of TV debates in UK general elections.

“This research is proof that televised election debates are good for our democracy.

“That over 80% of viewers said they talked about the QT special with their friends and family shows it has a positive impact on political engagement. And 40% said the programme made them more interested in the campaign.

“That’s good for all of us.”

Challenging test

Prime Minister Theresa May taking part in the Question Time Leaders Special from York. Photograph: Stefan Rousseau / PA

He added that the swing to back Mr Corbyn suggested the programme “may have had an impact on the final result – particularly when just a few hundred votes in swing seats shifted June’s outcome”.

Question Time presenter David Dimbleby said: “The findings of the election survey confirm what we have always believed – that a Question Time audience given the freedom to ask what they want is a challenging test for politicians.

“Head-to-head debates and one-on-one interviews both have their part to play in elections but the raw experience of facing a Question Time audience offers something quite different.

“Voters speaking from their own experience directly to party leaders expose evasion and test policies in a uniquely revealing way.”