Youth vote campaigners are warning of a democratic deficit in the general election as it emerged that the Cabinet Office will not provide funding to groups focused on increasing turnout among young and marginalised people.

As the electoral commission launches a campaign to increase voter registration before the deadline on 22 May, the Guardian has learned that funding provided by the Cabinet Office in past general elections will not be available this time because the pre-election period has already begun.

Lucy Caldicott, chief executive of the youth leadership organisation UpRising, said: “We are in an environment where many charities are already working really hard to get our campaigns to encourage young people to vote up and running but we are asking just how much of an impact we can make in such a short time.

“There is a real risk of there being a democratic deficit in this election due to the lack of notice and short campaign. Do we continue to focus on our core long-term activity or throw our assets behind getting a few thousand more votes out, as important as that is? We will of course encourage all those young people we work with to take part by voting on the 8 June.”

Young people could be left feeling ignored and marginalised as charities have to choose between risking their long-term financial stability and ploughing resources into getting out the youth vote. Campaigners say that as the election falls in the middle of the exams period, some students are unsure whether to register at their university address or at home.

The election also coincides with the Muslim month of Ramadan, raising questions about a further potential barrier for ethnic and faith minorities who are already under-registered.

After a huge push to get voters to register for the EU referendum, some organisations have been left with little in reserve to engage young people in an election that will shape their futures for the next five years and beyond.

Young people have been repeatedly accused of moaning about Brexit despite failing to vote in the EU referendum, with one estimate soon after the referendum claiming that only 36% of 18- to 24-year-olds had taken part.

But analysis by the London School of Economics of detailed polling conducted since the referendum by Opinium suggests turnout was as high as 64% among young people registered to vote, and that more than 70% of young voters choosing to remain in the EU.

Elisabeth Pop, voter registration campaign manager at the anti-fascism group Hope Not Hate, said: “The big question at this snap general election is: who will decide Britain’s future? With less than a month to go until voter registration ends, there is a real risk that students and certain other vulnerable groups will miss out on their chance of a voice.

“Our research clearly shows that traditionally underrepresented communities and social groups – such as students and young people, ethnic minorities and renters – remain at risk of not having a say come 8 June.”

In a series of emergency meetings in recent days, groups have been devising urgent action plans and putting themselves on a battle footing despite time and financial pressures.

The youth voter movement Bite the Ballot promises “weeks’ worth of unconventional activities” to get out the youth vote, and will be partnering with high-profile companies to reach as many young people as possible.

Hope Not Hate and Bite the Ballot will team up for TurnUp – eight days of concentrated action and a digital push in the run-up to the voter registration deadline; while UpRising will work with young people on its programmes to ensure they are registered and encourage them to get involved in the debate.

“The main thing we will be up against is voter fatigue,” said Kenny Imafidon of Bite the Ballot. “A lot of people don’t understand why we are going to the polls again. Our message is that there is power in participation. This election is not just about Brexit, it’s about big issues facing young people like housing, employment, education reform. Our role is not to tell people who to vote for, but get them to ask critical questions.”