An estimated 4,000 people were turned away from casting their vote in the five areas trialling controversial voter ID checks.

Analysis of figures released by electoral observers suggests 3,981 people were denied a ballot paper in the local elections due to not being able to provide relevant identification documents.

The figures show 1.67 per cent of voters in the pilot areas were unable to cast their vote, with people turned away in more than one in five polling stations across Bromley, Woking, Gosport, Watford and Swindon, where the pilot was carried out.

Labour urged the government to scrap the practice, saying it “undermined democracy” after it emerged during voting on Thursday that people had been prevented from casting their ballot.

The new analysis, carried out by the Electoral Reform Society (ERS), reveals the “shocking” scale of the problem, raising concerns that millions of people could be disenfranchised if the scheme is rolled out across the country.

One of those unable to vote was 76-year-old Peter White, who told The Independent he was “shocked” after being turned away from a polling station in Bromley because he did not have a bank card or passport.

Darren Hughes, chief executive of the ERS, said: “Britain prides itself on being a leading democracy – but it is a dark day for politics when thousands of blameless people turn out to vote only to be refused.

“Our estimates, based on evidence gathered by electoral observers, reveal the shocking scale of the problem. These trials have been shown up to be the chaotic, undemocratic mess many predicted.

“These findings are exactly what many feared: that this draconian measure would result in blameless individuals being disenfranchised. It is vital moving forward that these draconian trials are not a fait accompli for a national rollout.”

The figures did not take into account whether voters came back with the correct ID having initially been turned away. It is also impossible to know how many people were put off from entering a polling station altogether because of the new ID requirements.

Democracy Volunteers, the UK’s largest election observer group, collated the figures while carrying out extensive observations of the ID checks in 243 polling stations across the five areas the scheme was being piloted.

John Ault, director of the organisation, told The Independent 10 voters had been turned away within a 45-minute period at one polling station in Swindon, and that the issue appeared to disproportionately affect ethnic minority voters.

“Obviously there were always going to be teething problems, but I also think quite clearly that if you – whether intentionally or otherwise – exclude 1.5 to 2 per cent of the population, that is a significant problem,” he said.

“The process was quite well run. Staff were welcoming and generally helpful, they tried to assist people who didn’t realise they were required to bring ID.

“But the problem is some people clearly weren’t able to produce it, and we don’t know how many people didn’t come because they didn’t have it in the first place.”

Cat Smith, Labour’s shadow minister for voter engagement and youth affairs, clamed it was “impossible” for the government to justify rolling out the scheme.

“After completely ignoring a number of serious warning signs, the government decided to pilot discriminatory measures which denied people their right to vote,” she said.

“We cannot allow the Conservative Party to undermine our democracy, which is why Labour is calling on the government to scrap its voter ID plans as a matter of urgency.”

Campaigners had questioned the evidence on which the trials were based. Figures from the Electoral Commission show there were just 28 allegations of impersonation in 2017 out of nearly 45 million votes – or one case for every 1.6 million votes cast. Only one of these allegations resulted in a conviction.

Senior officials in trial areas expressed their concerns about the trials, while the government was criticised by the UK Statistics Authority for pushing misleading figures to support the need for the pilots.

Local elections 2018 – in pictures Show all 8 1 /8 Local elections 2018 – in pictures Local elections 2018 – in pictures Jeremy Corbyn outside a polling station in Islington Rex Local elections 2018 – in pictures Theresa May and her husband Philip arrive at a polling station to vote in local elections in central London AFP/Getty Local elections 2018 – in pictures Boris Johnson leaves after voting in London Reuters Local elections 2018 – in pictures Liberal Democrats leader Vince Cable with his wife Rachel at Twickenham polling station Rex Local elections 2018 – in pictures A man enters a polling station as voting begins in local government elections in London Reuters Local elections 2018 – in pictures A man fixes a sign to the door of a polling station as voting begins in local government elections in London Reuters Local elections 2018 – in pictures A poll clerk hangs a polling station sign outside the Victoria and Jubilee Halls in Hartley Wintney, Hampshire, some 45 miles west of London AFP/Getty Local elections 2018 – in pictures Voters at The Vyne polling station in Knaphill, part of the Woking borough, which is one of five councils working with the Cabinet Office to trial the use of ID in polling stations PA

A government spokesperson insisted the pilots had been a “success”.

“Voter ID is an important step to ensuring the public can have greater confidence in our democratic system and the success of yesterday’s pilots proves that this is a reasonable and proportionate measure to take,” he said.