Democracy campaigners have accused politicians of ignoring the issue of electoral reform in the general election campaign, arguing that “the signs of democratic decay are all around us”.

In a letter the Guardian on what they dubbed “democracy day” on Thursday, political reform groups called on parties to commit to a “constitutional convention” involving members of the public, to examine how to overhaul Westminster after the election. They said the issue of political reform had been dangerously absent from the campaign trail.

“For all the divisions on display in this election campaign, there’s one point nearly all voters agree on: the desperate need for reform in Westminster,” said the letter, signed by organisations including the Electoral Reform Society, Unlock Democracy, Make Votes Matter, and Compass.

“Yet despite many parties commenting on the need for change in their manifestos, the issue of political reform has been dangerously absent from the campaign trail.”

Polling commissioned by the Electoral Reform Society found that 85% of people feel that politics isn’t working, and 80% feel they have little or no influence on decision-making.

Of the more than 1,600 adults surveyed, just 2% said they felt democracy was working extremely well and could not be improved, or felt they had a great deal of influence over decision-making in the country as a whole.

“The signs of democratic decay are all around us – from an electoral system that wastes votes on an industrial scale, to the private members’ club that is the unelected House of Lords,” said the letter. “This year we’ve seen our parliament lunge from crisis to crisis. This election is a watershed moment for our democracy – inaction is not an option.”

The proposed constitutional convention would be led by a citizens’ assembly and would look at how power should be distributed in society. Citizens’ assemblies are large representative groups of people, selected in a similar way to a jury, to address a particular issue.

A recent example of the use of citizens’ assemblies was in Ireland where one was established to examine the issues of abortion, climate change, an ageing population, how referendums are conducted, and fixed-term parliaments. The assembly, which was composed of a chairperson and 99 citizens, met on weekends 12 times over 18 months.

Despite multiple requests, no spokesperson from Labour, the Liberal Democrats or the Conservatives is due to attend a debate organised by political reform groups about the future of democracy on Thursday at the People’s History Museum in Manchester.