Justice Secretary Michael Gove, a key figure in the referendum's Vote Leave campaign said that money sent to Brussels could be better spent on the NHS.
Speaking after Vote Leave launched its advert in Manchester claiming that £350 million, £50 million a day, is handed to Brussels, he said:
At the moment the money that we give to the European Union is spent by others, people we have never elected, never chosen and can't remove.
If that money is taken back, then that £50 million a day will be spent on British people's priorities and the NHS of course is top of people's list.
The £350 million figure has been disputed by other sources that claim it does not take account of the UK's agreed rebate.
Boris Johnson has criticised Barack Obama who plans to urge the UK to remain in the EU referendum branding it "hypocritical".
The EU referendum campaign has officially begun - ten weeks before Britain decides whether to leave the union.