Members of Parliament filled the House of Commons to debate the government's proposed EU referendum, as parties clashed over the future of the UK and the EU.
Foreign secretary Phillip Hammond introduced the EU Referendum Bill, calling it a "simple but vital piece of legislation". He said that the EU is often seen as "something done to [British citizens], not for them".
"EU's democratic mandate is wafer thin"
He pointed to the lowest ever turnout in last year's European referendum, where it dropped to 13 per cent in some EU countries.
He said the Conservatives would deliver on their promise to give voters an in-out referendum, claiming that the way the EU has changed since the last referendum in 1975 had "eroded the democratic mandate for our membership to the point where it is wafer thin and demands to be renewed".
While the bill had support from the main opposition, the government faced unrest from its backbenchers.
Former Tory chancellor and pro-European Ken Clarke said he would not vote for the Referendum Bill. He said:
The idea that we somehow advance our future propserity by withdrawing from the biggest, organised trading bloc in the world, at the same time the Conservative Party being an advocate of free trade wherever can be obtained, will be an absurdity.
Ukip MP Douglas Carswell was also vocal during the debate, while supporting the referendum.
Tried to intervene on Foreign Secretary over 40 times. Ignored. What chance will phoney Phil Hammond give Out campaign a fair hearing?— Douglas Carswell (@DouglasCarswell) June 9, 2015
"The answers lie in cooperation"
Hilary Benn, shadow foreign secretary, said that Labour supported the referendum, but also supported Britain's membership of the EU.
He said the referendum presented a "clear and simple question", but one whose "answer will a profound impact" on the country.
Benn mocked Cameron on his perceived u-turn about whether ministers should be given the freedom to campaign for British withdrawal of the EU.
On jobs, economic growth, climate change and terrorism, Benn said, "the answers lie in cooperation" and "work[ing] with others".
Giving 16 and 17 year olds the vote
There was significant debate over the franchise of the referendum, with 16 and 17 year olds not being allowed to vote.
Green MP Caroline Lucas was among those to voice concern over not including 16 and 17 year olds in the vote, and Labour has proposed an amendment to the bill on the matter.
Former SNP Scottish first minister, Alex Salmond, dubbed the bill "nonsense and a contradiction".
The EU referendum Bill fails to meet gold standard set in #indyref in terms of inclusivity and democratic participation.— Alex Salmond (@AlexSalmond) June 9, 2015
Speaker John Bercow said that "some dozens" of MPs wanted to speak in the debate, and imposed a time limit on MPs' speeches.
Parliament is due to vote on the matter later this evening, with the bill expected to pass its second reading.
Current opinion polling suggests that the British people wish to remain in the EU.