Campaigners wanting to be involved in promoting the outcome of the vote on whether Britain should stay or leave the 28-nation bloc will have to register with the Commission. They will also have to report all loans and donations that are over 7,500 pounds ($10,700).
A law on the referendum was adopted on December 17, 2015. The exact date of the vote is not known yet. The question will be "Should the United Kingdom remain a member of the European Union or leave the European Union?"
Last month, Cameron confirmed that UK ministers would be allowed to campaign for either side in the EU membership referendum.