The Telegraph called the victory at approximately 11:50 p.m. Eastern time with just under 80 percent of the voting areas declared.
A record 72.2 percent of the population turned out to vote on the referendum, the Telegraph said.
The results began to trickle in after 9 p.m. local time and remained largely even. The Leave camp, however, began to pull away as 50 percent of the reporting districts declared.
Results played havoc with the British Pound, which dropped from $1.50 against the U.S. Dollar to below $1.40 within the span of five hours, according to The Wall Street Journal.
The results of the referendum are not legally binding and require Parliament to repeal the act passed in 1972 that allowed the U.K. to enter the European Union, ABC News reported.
Those advocating exiting the EU argue it will allow Britain to take back control of its borders and that it could help Britain's economy, already strong as the fifth largest in the world, to expand without having to adhere to the numerous rules on business and charges in EU membership fees.
Many economic experts in the United States warned that if Britain exits the EU, the uncertainty of the global financial impact could send stocks diving.
Britain last voted on whether to remain in the EU, an economic and political partnership made up of 28 European countries, in 1975.
Click here to read The Telegraph's coverage.
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