Europe

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

  • Nigel Farage, the leader of the UK Independence Party, poses for the media as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU outside the door of 10 Downing Street in London, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)

    Nigel Farage, the leader of the UK Independence Party, poses for the media as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU outside the door of 10 Downing Street in London, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)  (The Associated Press)

  • Nigel Farage, the leader of the UK Independence Party, knocks on the door of 10 Downing Street in London, as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)

    Nigel Farage, the leader of the UK Independence Party, knocks on the door of 10 Downing Street in London, as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)  (The Associated Press)

  • Nigel Farage, the leader of the UK Independence Party, poses for the media as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU outside the door of 10 Downing Street in London, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)

    Nigel Farage, the leader of the UK Independence Party, poses for the media as he returns and rejects a government mailshot leaflet stating their reasons for the UK to stay in the EU outside the door of 10 Downing Street in London, Friday, April 15, 2016. Britain is to hold a referendum on their EU membership on June 23. (AP Photo/Matt Dunham)  (The Associated Press)

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.