Britain's pro-Europeans prepare "Yes" campaign group: Sources

Supporters of Britain's membership of the European Union will create a new group shortly to run the "Yes" campaign for a referendum Prime Minister David Cameron has promised by the end of 2017, four sources familiar with the plan told Reuters. 

The new group aims to focus the efforts of disparate pro-Europeans who fear a British exit from the 28-nation bloc it joined in 1973 would diminish London's clout, hammer the world's fifth largest economy and trigger a new crisis in the EU. 

Cameron, whose Conservative party won a surprise majority in the May 7 election, has promised to renegotiate Britain's EU relationship. Some campaigners expect the referendum well before his self-imposed deadline, possibly next year. 

"A new organisation to bring together the "Yes" campaign will be launched in the very near future," said a senior member of the group who spoke on condition of anonymity as the plans have yet to be formally announced. 

"This will be the foundation of the "Yes" campaign," said the source, declining to address its leadership or financing. 

A second source said the "In" campaign would be kept at arm's length from the Cameron government to enable it to garner cross-party and popular support. 

The sources differed on the countdown to an announcement, with some citing weeks and others months. 

A third person involved in the project said the group would be unveiled soon because "the landscape is changing quite fast", but the exact timing depended on the progress of Cameron's talks with other EU leaders. 

A fourth source said it would be created within months but the leadership of the organisation had yet to be decided. Many pro-European British politicians tend to be of the older generation and...