In or out? UK's EU referendum campaign officially kicks off

Campaigning for Britain's European Union referendum has officially begun — though Britons could be forgiven for thinking it has been going on for months.

Friday marks the start of the official 10-week campaign ahead of a June 23 vote on whether to leave the 28-nation bloc.

Unofficial campaigning has been going on since Prime Minister David Cameron secured an agreement on revised EU membership terms for Britain in February. He says that deal means the U.K. should stay in.

During the official campaign period, the groups Britain Stronger in Europe and Vote Leave will each get free TV ad slots, receive some public funding and be able to spend up to 7 million pounds ($10 million) of their own money.