Former M&S boss Lord Rose claims the UK risks 'leaping into the unknown' if it pulls out of the European Union.
He chairs the formal campaign to keep Britain in, which launched earlier ahead of the referendum on their EU membership before the end of 2017.
Ukip leader Nigel Farage is campaigning for a vote to leave.
He says it is a greater risk to stay in.
"Taking back control of your life, taking back control of your borders, doing what every other country in the world does which is to make their own trade deals and decide their own future - I don't see that as the risk, I see the risk Lord Rose, as being shackled to the corps that is now the European Union."