Britain's FTSE 100 rose 2.2% in early trading

No benefit from 'prolonged limbo' Dutch defence minister tells EU parliament

"Today, on behalf of the 27 leaders I can say that we are determined to keep our unity as 27," Tusk said.

"It's very close; nobody knows what's going to happen," Cameron told Wednesday's Financial Times, with opinion polls showing the rival camps neck and neck.