Pro-EU Home Secretary Theresa May used her first major intervention in the referendum debate to argue Britain should stay in the 28-nation bloc, but pull out of the European Convention on Human Rights.
Mrs May’s comments appeared to put her at odds with Prime Minister David Cameron, who has previously said he is seeking to reform the Convention, but rules nothing out if this proves impossible.
Asked whether Mrs May was speaking on behalf of the Government, the PM’s official spokeswoman would say only that she was “setting out her views as Home Secretary”.
Brexit campaigners said that Britain could not ditch the Convention – which is operated by the separate Council of Europe – without breaching EU treaty obligations.
And Liberal Democrat leader Tim Farron accused the Home Secretary of using the referendum debate to further her claim to be next Conservative leader.
Meanwhile, US president Barack Obama followed up his warnings on the economic risks of Brexit with an appeal for a “united” Europe to help drive global security, democracy and prosperity.
Speaking in the German city of Hanover ahead of a summit with Mr Cameron and other EU leaders, the president acknowledged that European unity involved “frustrating compromise”, but hailed the multinational union as “one of the greatest political and economic achievements of modern times”.
A retreat from European unity and the reconstruction of the “barriers and walls” which divided the continent in the 20th century would risk halting progress towards democracy and tolerance elsewhere in the world, the president warned.
“A strong, united Europe is a necessity for the world because an integrated Europe remains vital to our international order,” he said.
Mr Obama’s intervention came as Brexit’s biggest hitters sought to regain the referendum initiative by putting immigration at the top of the agenda.
Justice Secretary Michael Gove warned the UK faces a migration “free-for-all” constituting a “direct and serious threat” to public services such as the NHS unless it breaks away from Brussels.