The referendum on Britain’s membership of the European Union may face a legal challenge after the government extended the deadline for registering to vote by two days. Britons had originally been given until midnight Tuesday to register to vote in the historic referendum, which takes place in two weeks’ time. But as the deadline loomed on Tuesday night the government’s online registration system crashed, leaving thousands unsure as to whether they were registered or not. In response the government yesterday legislated to extend the deadline until midnight tonight. According to Leave.eu co-chairman Arron Banks, that extension may leave the results of the referendum open to legal challenge. “For the Government to alter election law during an election period is absolutely unprecedented and unconstitutional,” Mr Banks said in a statement. Speaking to Radio 4’s Today program this morning, he confirmed that he was exploring the possibility of mounting a legal challenge, saying: “We’ve got lawyers that are looking at it at the moment. “They are tending to say it’s unconstitutional because once you’ve set the rules you can’t really change it halfway through, and Parliament really shouldn’t be doing this.” Mr Banks, along with many other leave campaigners, have accused the