UK elections are “close to a tipping point” where they lose legitimacy because of plummeting voter turnout among renters and non-graduates, an influential thinktank has said.

Analysis by the Institute for Public Policy Research (IPPR) found that the gap in turnout between those with and without university degrees grew to 11 percentage points in the 2024 general election – double that of 2019.

The turnout gap between homeowners and renters grew by nearly a quarter between the 2017 and 2024 elections, to 19 percentage points.

The findings suggest a growing disillusionment with politics among certain social groups, which is leading to increasingly unequal elections.

Parth Patel, an associate director of democracy and politics at IPPR, said: “We are close to the tipping point at which elections begin to lose legitimacy because the majority do not take part. That should be ringing more alarm bells than it is.”

Turnout inequality in the 2024 election was 11 percentage points between the top and bottom third earners and between people in working-class and middle-class jobs, which was largely unchanged since 2015.

The turnout gap between 18- to 24-year-olds and over-60s was 21 percentage points, a measure that has also remained stable, according to the analysis.

The data is likely to provoke concern among Labour strategists. Morgan McSweeney, Keir Starmer’s chief of staff and most influential adviser, built his 2024 election strategy around winning over voters without university degrees.

Party figures have turned their attention to combating the rise of Nigel Farage’s Reform UK, which came second in 89 Labour-held seats, including in many of the party’s former industrial heartlands in the north of England.

Labour committed to several franchise-boosting measures in its manifesto, including making voter registration easier, lowering the voting age to 16 and tightening the rules around political donations. The party has declined to unpick voter ID rules introduced by the Conservatives but has said it will increase the types of ID accepted at polling stations.

It has not pledged to introduce automatic voter registration but the Guardian reported in June that it was drawing up plans to do so. All these policies would form part of a democracy bill, which is in the early stages of development.

The IPPR called for bolder measures including a new civic duty to staff polling stations, which would be akin to jury service. The thinktank said that without action to improve participation in democracy, populist movements would continue to gain more traction even if the economy was doing well.

Only one in two adults living in the UK voted in the July 2024 general election, the thinktank’s analysis showed, which was the lowest share of the population to vote since universal suffrage. Among registered voters, only three in every five cast a ballot.

The IPPR recommended four policies that it said would be effective in raising turnout, narrowing inequality and could feasibly be implemented in this parliament. These were:

• Lowering the voting age to 16.

• Implementing automatic voter registration.

• Introducing a £100,000 annual cap on donations to political parties.

• Creating an “election day service”.

This latter would involve recruiting poll workers from the population by lot, similar to selecting citizens to do jury service.

Other policy suggestions included moving polling day to a weekend or making election days a public holiday, and scrapping the voter ID requirements introduced by the Conservatives.

The IPPR also said the government should consider enfranchising the 5 million long-term tax-paying residents who are not citizens of the UK, Ireland or Commonwealth countries.

Another suggested change is redrawing constituency boundaries based on the entire adult population of an area, not just registered voters.

Finally, the thinktank recommended bolstering the Electoral Commission’s powers to investigate candidate rule-breaking and impose sanctions, including fines of up to £500,000 or 4% of campaign spending.

Last month the Guardian reported that ministers were considering proposals from Vijay Rangarajan, the chief executive of the elections watchdog, to strengthen the rules around political donations to protect the electoral system from foreign interference.

Rangarajan said linking donations to political parties to the UK profits of companies owned by foreigners was one of the urgent changes needed to retain the trust of voters.

The move, which the government is looking at, could cap the amount that Elon Musk could donate through the British arm of his social media company X (formerly Twitter). There has been speculation that Musk, who is an ally of Donald Trump and a fierce critic of Starmer, could make a $100m (£80m) donation to Reform.

Ryan Swift, an IPPR research fellow who co-authored the report, said: “The widening turnout gaps between renters and homeowners, and graduates and non-graduates, highlight a glaring blind spot in tackling political inequality.

“To rebuild trust and strengthen democracy, we need bold reforms like votes at 16, automatic registration and fairer electoral rules.”