The Party’s European Spokesperson raised concerns after the deadline was originally extended for 24 hours across the United Kingdom, only for Northern Ireland to be excluded a few hours later.
Stewart Dickson MLA said: “In less than two weeks, voters across the UK are facing one of the biggest decisions of our generation, and one that has the potential to have a dire effect on our economy.
“Yet new voters who have turned 18 since the May election faced mixed messages from The Electoral Commission in the rush to get registered on time – this is simply not good enough.
“I seriously question why the Northern Ireland Office needed to get involved, creating chaos and confusion. They must clarify immediately why they thought it was ‘not sensible’ to include Northern Ireland in the extension.
“While the Secretary of State is firmly in the Brexit camp, Northern Ireland as a whole is expected to return a large percentage in favour of remaining part of the EU. Everyone of voting age deserved the opportunity to register to take part in this important decision.”