LONDON: The former chief executive of retail chain Marks & Spencer is heading a campaign to persuade Britons to stay in the European Union, arguing Monday that quitting could leave the country isolated, less secure and economically weakened.

Ex-M&S boss Stuart Rose said that "leaving Europe is a leap into the dark and I don't believe that is a risk worth taking."

"To claim that the patriotic course for Britain is to retreat, to withdraw and to become inward-looking is to misunderstand who we are as a nation," Rose said at a London launch for the Britain Stronger in Europe group.

The campaign is backed by former Prime Ministers John Major, Tony Blair and Gordon Brown and includes ex-British Army chief Peter Wall and soccer executive Karren Brady.

Britain will hold a referendum by the end of 2017 on whether to leave the 28-nation EU after more than 40 years of membership. Prime Minister David Cameron says he will argue to stay in as long as he can negotiate looser ties with the bloc.

But other EU countries have limited patience for Britain's demand for special status. And the migrant crisis — which has seen European countries struggle to deal with hundreds of thousands of new arrivals from the Middle East and Africa — has emboldened those who want Britain to strengthen its borders.

The pro-Brexit side has been beset by division, however, some of it focused on the role of Nigel Farage, leader of the right-wing UK Independence Party. He is a popular but polarizing figure seen by some as too extreme to sway moderate voters.

Two campaign groups, Vote Leave and Leave.EU, have been formed to argue the case for leaving the EU. Vote Leave includes Conservative and Labour politicians as well as UKIP's only lawmaker, Douglas Carswell. The Leave.EU organisation is funded by a wealthy UKIP donor.

Farage said he supported both groups and accused Rose of "turning the truth on its head" by arguing that remaining in the EU is a patriotic move.