Campaigners have raised fears that bouncers could be placed at some polling stations to turn away voters who do not have the right ID.
Supporters of Open Britain and Unlock Democracy gathered in Westminster on Tuesday to demand new voting registration rules are scrapped.
Under the regulations, voters will be required to have photographic ID such as passports or driving licences when they cast ballots at May’s local elections.
The groups warned as many as two million people may be turned away as they do not currently have the appropriate ID.
Only around 32,000 applications have been made since the scheme launched in January – an average of just 500 a day, according to the campaign groups’ research.
Speaking at a protest outside Parliament, Open Britain chief executive Mark Kieran told the PA news agency: “Democracy is struggling in this country. People are disenfranchised with it. Sadly it does not take a lot to stop ordinary members of the public when it comes to voting.
“Even just the fact that people need to remember to carry their ID when they leave to go to work that day. It is likely that people will find themselves intending to vote and not being able to because they simply forgot to bring their voter ID. There are a lot of people who have not heard about this and will get a big surprise.”
He claimed the voting cards are a barrier to democracy and that people could get angry or frustrated when they are turned away at polling stations.
Concerns have also been raised about the impact this could have on local seats which can be decided by a handful of votes.
Mr Kieran added: “I imagine we will have a lot of confusion and confusion is not helpful when you are dealing with something as fundamental as democracy. I think it could quickly turn to anger. It’s not something that should ever be considered when casting your vote. It should be as easy and straightforward as possible to do that.
“We are only reaching the point where people are starting to realise the practical implications of this. The bouncer thing is astonishing. Think about that for a second. A local authority employing bouncers to be on site when people are casting their vote. It’s crazy in this country.”
“At least one local authority is going to be hiring bouncers as they are worried that there will be altercations with people who will turn up, and have been turning up and voting there for 30 or 40 years, and then get angry when they’re told ‘Sorry, you haven’t brought your ID so you won’t be voting here today’.”
He added: “Even one voter turned away is one too many. Now thanks to a disastrous rollout, the integrity of our elections in May is now at risk, with tens of thousands of eligible voters likely to be turned away at polling stations.”
Campaigners believe up to 4% of voters across Britain do not currently have a valid form of photo ID which is needed to vote at a polling station.
London has the most adults who do not have recognisable photographic ID (around 417,086 adults), followed by the South of England (195,384 adults) and Yorkshire and Lincolnshire regions (189,190 adults), according to their research.