Amid growing Euro-scepticism and pressure from anti-EU parties like UKIP, the Conservative Prime Minister David Cameron and his party promised voters in the 2015 general elections that if their party won, then a referendum would be organised regarding UK’s membership in the EU.
In 2013, Cameron first promised British voters that he would renegotiate the terms of EU membership. These renegotiated terms were reached in early 2016. However, there were no significant changes in the EU-UK relationship apart from the already established opt-outs and the UK rebate. At the same time, Parliament had already approved the referendum and campaigning had already started.
The official group which was approved to organise the Remain campaign was Britain Stronger in Europe, while Vote Leave was the group which organised the Leave campaign.
The Remain campaign was mostly supported by liberals and members of the Labour Party, while the Conservative Party was split on the issue. The Leave campaign was supported by Euro-sceptics and some Conservatives, including MP Boris Johnson who became a frontman for Vote Leave.
The Conservative Prime Minister supported the Remain campaign, but the members of his party were free to endorse whichever campaign they agreed with. In general, the Conservative Party as a whole adopted a neutral position, avoiding getting too involved in any of the campaigns.
Apart from the two official campaigns, UKIP organised a separate campaign aimed at persuading voters to opt for leaving the EU. Their campaign was titled Leave EU.
Each campaign was further endorsed by different business, media, and trade unions, leading to both campaigns having support across all segme...