A challenge against the legality of the EU’s Brexit negotiations brought by a 97-year-old British veteran is to be heard by five judges at the European court of justice this week.

Harry Shindler, who lives in Italy, and 12 other Britons who live in various member states, will argue that the 2016 referendum was discriminatory and illegal because they – and more than 1 million other British expatriates – were denied a vote.

The hearing in Luxembourg on Thursday has the capacity to derail Brexit, Shindler believes, although his previous legal attempts to widen the franchise to include all Britons living overseas failed at the UK supreme court shortly before the poll two years ago.

Lawyers for Shindler and the other claimants allege they were treated like “second-class citizens” and unfairly deprived of their right to vote merely because they exercised their freedom of movement within the EU. They were discriminated against on the basis of their residence, it is said.

“I’ve been asked to go to Luxembourg but I’m 97 and I restrict my travelling,” Shindler told the Guardian from his home in Porto d’Ascoli above the Adriatic coast. “I’ve told them I will be by my telephone if they require me to testify.”

London-born Shindler served in Italy during the second world war and took part in the 1944 liberation of Rome. He married an Italian and went back to live there on retirement in 1982. He was awarded an MBE in 2014 for his services to Anglo-Italian relations.

“We are called expatriates,” Shindler added, “but we are not all old or retired. We are journalists, interpreters, teachers and do all sorts of other jobs – we are representative of the general run of the British nation.”

His case is being presented by a Bordeaux-based lawyer, Julien Fouchet of Cornille-Pouyanne Avocats, who will tell the court the EU’s negotiations with the UK over Brexit should not take place because the British negotiators are not representative of the British people.

The vote, he will say, was illegal because those most affected by the decision to leave the EU were denied the opportunity to participate and express their opinions.

“By adopting the contested decision [the EU] has allowed a withdrawal procedure to be initiated without expatriate European citizens having had the opportunity to set out their views on the possible loss of their European citizenship,” Fouchet’s submission to the court states.

“The right to be heard and to express one’s opinion by way of a vote in the event of an election with a European scope has thus not been respected.”

The European council maintains that Shindler and his colleagues do not have legal standing to bring the case. Wednesday’s hearing will consider the admissibility of the claim.

Shindler added: “If we win this, that’s the end of Brexit because Mrs May will arrive with her negotiators and there will be no one for her to negotiate with.”

In 2016, Brenda Hale, then deputy president of the supreme court, rejected the application to expand the franchise on behalf of Shindler partially on the grounds that there was no interference with the right of free movement under EU law.

There is a 15-year time limit on British expatriates being able to register as overseas voters. The government has said it will support a private member’s bill introduced by the Conservative MP Glyn Davies that would do away with that time restriction.

The bill has had its second reading and is at committee stage. Labour, however, had said it would oppose the bill because it would cause too much administrative work.

Shindler, who has been a member of the Labour party since 1936, said he supported the bill and hoped it would enable up to 5 million Britons living overseas to vote in future elections. “There should be no time limit about British,” he said. “You are British for life.”

• This article was amended on 3 July 2018. Because of an error in information distributed by the European court of justice, an earlier version said the hearing would be on Wednesday (4 July). This has been corrected to say Thursday.

