British Prime Minister David Cameron says the results of a referendum on Britain's exit from the European Union will be final.
"This is a vital decision for the future of our country and I believe we should also be clear that it is a final decision," Cameron said during an address in Parliament Monday.
He dismissed calls for a second referendum by London Mayor Boris Johnson who suggested the vote to leave could help Britain renegotiate its terms with the EU.
"An idea has been put forward that if the country votes to leave we could have a second renegotiation and perhaps another referendum. Mr. Speaker, I will not dwell on the irony that some people who want to vote to leave apparently want to use a leave vote to remain," Cameron said.
WATCH: London Mayor Johnson wants Britain to break with EU
Johnson, one of Britain's most popular but unconventional politicians, is the highest profile Conservative to split with fellow Conservative Cameron over staying in the 28-nation European Union.
Officials from the office of the prime minister said if the June 23 referendum initiative passes, Cameron would invoke article 50 of the Lisbon treaty, which sets in motion a two-year negotiation process where the European Union presents Britain with a final package to which they can either accept or reject.
Britain would also lose its seat on the European Council during this period.
Cameron has warned that Britain's exit from the bloc would threaten the country's economic and national security.
EUROPOL chief Rob Wainwright said an EU exit would leave the more vulnerable to attacks by terror groups and organized crime gangs.
No country has ever left the European Union.
Six of Cameron's Cabinet ministers say they also support Britain leaving the bloc, but former Prime Ministers Tony Blair and John Major are supporting the "stay" campaign, as are major companies, much of the Labor Party, major trade unions and Britain's international allies.