Mr Corbyn faced questions over his commitment to the campaign after giving a speech in which he attacked the Government’s “prophecies of doom” about the potential economic fallout of Brexit.
The Leave camp latched on to the speech and claimed it had caused “chaos” in the Remain campaign, but the Labour leader denied he was “muddying the waters” on his party’s stance – insisting he was making a “distinctive” case to stay in the EU.
In a set piece TV event, Mr Cameron did not rule out sharing a platform with Mr Corbyn, and praised his speech.
But Mr Miliband urged Mr Corbyn not to fall into the “Labour trap” of being half-hearted about Europe and told him to make a “progressive and positive” case with “energy and drive”.
Writing for the Times Red Box, he said: “In 2006, David Cameron called on the Conservative Party to ‘stop banging on about Europe’. The Tory trap was to be obsessed with Europe. As the referendum debate shows, the schisms are deep and personal.
“Labour’s trap is different. It is to be half-hearted about Europe. In 1962, Hugh Gaitskell answered Yes or No to the Common Market by saying ‘If…’. There is no room for such hesitation today.
“There are overwhelming cross-party reasons of national interest – to do with national security and foreign policy for example – for Britain to be part of the EU.
“But there are also distinctive centre-left arguments to vote to Remain. In the last three weeks of the campaign, they deserve to be given full vent. There is a progressive and positive as well as patriotic case that can be made with energy and drive.”
He added: “When Gaitskell finished his speech in 1962, his wife Dora reportedly told him that ‘the wrong people were clapping’. Labour supporters in Britain, with the party out of power at national level, cannot afford the wrong people to be clapping on the 24th June.
“I have been happy to share a platform with the Prime Minister to make the case for Britain’s membership of the EU. Where centre-right and centre-left agree, we should say so.
“But we also have something distinctive to say, and we should say it. That is why I am campaigning today with Alan Johnson, to rally a strong Labour vote in a cause that speaks to our hearts as well as our heads.”