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Britain will vote on whether to leave the EU on June 23

Tuesday is the voter registration deadline

CNN  — 

Hundreds of thousands of voters are signing up for a chance to weigh in on whether Britain should remain in the European Union.

On Monday alone, about 226,000 people submitted applications to take part in the June 23 referendum, according to a British government website.

That’s more than six times the number of people who signed up on one day a week before.

A possible reason for the surge: Tuesday is the last day for people to submit voter registration details in time to take part in the vote.

Brexit vote: A short guide

Younger people make up by far the largest group registering at the last minute, according to the data. Of the 226,000 who registered Monday, more than 148,000 were under 35. That could be significant, because polls suggest young people are more likely to vote to remain in the EU than are older people.

The government website provides live data of the numbers of people currently using the voter registration page; at one point earlier Tuesday more than 14,000 people were online at the same time.

With polls showing the race is too close to call, rhetoric is ramping up.

“It’s a roller coaster. … There’s no other way to say it,” said Nic Robertson, CNN International diplomatic editor.

British Prime Minister David Cameron made a fresh appeal this week for voters to keep the UK in the EU. A vote to leave would put a bomb under the British economy, Cameron said, accusing “Brexit” campaigners of performing an economic con trick on the public.

“There’s a passionate debate taking place in our country, and we should be proud of the fact that this is an enormous exercise in democracy and an enormous exercise in sovereignty, but we must make this decision on the basis of facts and arguments,” Cameron told reporters Tuesday.

Leave the EU or stay? Two British lawmakers weigh in

If Britain votes to leave the EU, Cameron will have to inform other European leaders formally, triggering two years of complex exit negotiations.

If Britain votes to remain, Cameron will have to make a reformed relationship with the EU work.

‘Brexit’ foes trade barbs on race as debate heats up

CNN’s Maggie Lake and Mark Thompson contributed to this report.