The campaign for the UK to remain in the EU, Britain Stronger in Europe, has launched this morning at an event in east London.
Business figures took a leading role in this morning's event, which included a campaign video featuring Easyjet chief executive Carolyn McCall saying, "Everything is easier because of Europe."
Led by former Marks & Spencer chief executive Lord Stuart Rose, the group also counts Apprentice star Baroness Karren Brady and RLM Finsbury founder Roland Rudd among its board members.
In a speech at this morning's event, Rose acknowledged he is not the most ardent Europhile, saying: "I am not an uncritical fan of the European Union, far from it."
But he added: "Wanting reform is far from wanting to leave."
Rose argued that Britain's EU membership added value to the UK economy – but stumbled over his words and said in error that being in the EU saves each taxpayer £485m per year. It is understood that he meant to say £450 is saved for each Briton.
And in a claim later repeated at the event by former BBC economics editor Stephanie Flanders, Rose likened a so-called Brexit to a "leap in the dark", saying: "We know our economy would take a hit, but we don't know how bad that hit would be."
As part of a panel discussion that also included Innocent drinks founder Richard Reed, Flanders said: "If anyone tells you they know what the other side of 'no' looks like, they're lying."
The cross-party campaign also has the backing of a swathe of politicians, including Policy Network chairman Lord Peter Mandelson, former Conservative minister Damian Green and current Green MP Caroline Lucas – not to mention former Prime Ministers Tony Blair, Gordon Brown and Sir John Major.
Former Prime Ministers were not on hand at this morning's launch, but Lucas did attend the event, as did former Liberal Democrat leader Lord Paddy Ashdown.
It is widely expected that Prime Minister David Cameron will take the helm of the campaign closer to the In/Out vote. Cameron has promised a referendum by the end of 2017, following a period of renegotiation.
Dominic Cummings, campaign director of Vote Leave, slammed the Britain Stronger in Europe campaign, saying it was "led by people who told us Britain would be doomed unless we ditched the pound.
"They've learned nothing from the disasters of the euro project and the inability of the EU to cope with the economic and technological forces changing the world," he added.