Thousands of voters in the May local elections are at risk of being disenfranchised because of “cynical” rule changes that make photo ID compulsory, Labour’s metro mayors argue. Mayors including Sadiq Khan in London, Tracy Brabin in West Yorkshire and Andy Burnham in Greater Manchester have come together to raise awareness of changes they say are a “brazen assault on our democracy”. The new system, they argue, is a Tory attempt to make it easier for the Conservative party to win and are “inspired by the voter suppression tactics of the US Republican party”. Last year’s local elections were the first ever in Great Britain to require voters to show photo identification. The same system will be in place on 2 May when voters in England and Wales head to the polls to elect about 2,600 local authority councillors, 39 police and crime commissioners and 10 metro mayors. All seven current Labour metro mayors have signed a joint letter condemning the changes and encouraging people to make sure they take valid photo ID. The May elections are the last ones before the general election and come, the mayors say, when there has never been so much anger at the Tories. “What the Conservatives won’t tell you is that they’ve changed the rules of the game to make it easier for them to win. For the first time, voters in mayoral elections must show valid photo ID at polling stations to be allowed to cast their ballots,” the mayors say. They point to comments by Jacob Rees-Mogg that suggested the changes were an attempt to gerrymander election results in favour of the Conservatives. Rees-Mogg told the National Conservatism conference: “Parties that try and gerrymander end up finding their clever scheme comes back to bite them, as, dare I say, we found by insisting on voter ID for elections. “We found the people who didn’t have ID were elderly and they, by and large, voted Conservative, so we made it hard for our own voters and we upset a system that worked perfectly well.” The mayors say the new rules are “even more cynical” in that only certain types of photo ID can be used. “While older people’s travelcards are eligible to use, many forms of identification used by young people, such as a young person’s railcard, are not allowed.” The letter continues: “It is vital that these changes – inspired by the voter suppression tactics of the US Republican party – don’t lock thousands more people out of our democracy on 2 May. We can’t let the Tories succeed in disenfranchising people, regardless of their age, ethnicity or the part of the country they live in. “Our message to every voter across the country today is clear – make sure you have the required valid ID. We must stop this brazen assault on our democracy.” The letter has also been signed by the metro mayors Steve Rotheram (Liverpool city region), Nik Johnson (Cambridgeshire and Peterborough), Dan Norris (West of England), Oliver Coppard (South Yorkshire) and by Claire Ward, Labour’s mayoral candidate for the East Midlands. The mayors point out that people without valid photo ID can go online and get it for free, but the deadline to apply for a voter authority certificate is Wednesday 24 April.