The former chief executive of retail chain Marks & Spencer is heading a campaign to persuade Britons to remain part of the European Union.

Stuart Rose leads the Britain Stronger in Europe group, which launched Monday and will brand those who want to leave the EU "quitters." The campaign is backed by former prime ministers John Major, Tony Blair and Gordon Brown.

Britain will hold a referendum by the end of 2017 on whether to leave the 28-nation EU. Prime Minister David Cameron says he will argue to stay in as long as he can negotiate looser ties with the bloc.

Two pro-Brexit campaign groups have been formed. Vote Leave includes politicians from the Conservative, Labour and U.K. Independence parties, while Leave.EU is funded by a wealthy UKIP donor.