BREXIT would be a “disaster” for most ordinary Britons because the Conservatives could not be trusted to protect workers' rights, Jeremy Corbyn will warn today.

In a speech in London, the Labour leader, will insist the party is "overwhelmingly for staying in" because the EU has brought investment, jobs and rights.

He will say: "It's important to understand the benefit of these gains. It means workers throughout Europe have decent rights at work, meaning it's harder to undercut terms and conditions across Europe."

Noting how a Tory government would be in charge of negotiating Britain’s exit if there were an Out vote, Mr Corbyn will add: “We could not rely on them to protect the workplace rights that millions rely on; a Tory Brexit negotiation would be a disaster for the majority of people in Britain."

Ahead of David Cameron’s first EU TV event tonight when the Prime Minister will face a live audience on Sky TV, leading Outer Michael Gove claimed a British exit from the EU would be a process of "evolution not revolution" and that those "stoking up Project Fear" would be surprised by the prevailing "calm and stability" and "sense of optimism" in the event of a Brexit vote on June 23.

The Justice Secretary, who himself will face a live Q&A on Sky TV tomorrow night, predicted Europe would "knuckle down" to deal with the reality of a UK departure, saying: "Overall, the changes we see will be a process of gradual divergence, not sudden turbulence."

The Scot claimed it was "absurd to suggest" the EU would seek to put up trade barriers in a "fit of pique," adding it would be clearly in the interests of the remaining 27 member states to continue trading freely with Britain. "You do not close the shop to your best customer," added Mr Gove.

In a separate development today, his Tory colleague and fellow Brexiter, Liam Fox, the former Defence Secretary, will in a speech warn

that young people will be forced to live with their parents for longer if the UK does not leave the EU because of increased pressures on housing caused by the uncontrolled influx of immigrants.

But Liberal Democrat leader Tim Farron, speaking for Stronger In, insisted: “A vote to Leave Europe will destroy young people’s hopes of getting on the housing ladder.”

Meantime, as the RSPB and WWF, which have 1.7 million supporters, came out this morning for Remain, Mr Cameron said: "EU membership underpins many crucial environmental protections in the UK while amplifying our voice in the world on vital issues like cutting global emissions.”

The RSPB made clear it would not tell supporters how to vote but Mike Clarke, its chief executive, noted: "As the Prime Minister rightly points out, UK membership of the EU has benefited nature and the environment in ways that would be hard to replicate if we left.”

Elsewhere, the In-Out row over immigration took a new twist.

Vote Leave insisted a proposal to bring in a post-Brexit Australian-style points-based system – which Ukip also supports – would ensure a "fairer" and “more humane” immigration system that would end the EU’s free movement principle as it currently applies to the UK and would ensure skilled workers who spoke good English filled vacancies.

But after George Osborne dismissed the idea as “fantasy politics”, claiming the proposal would not work and would actually increase immigration, Mark Rutte, the Dutch Prime Minister, warned any such new system imposed by the UK would see retaliatory action on the continent, sparking an immediate “race to the bottom” economically.

Also today, the Institute and Faculty of Actuaries published a report, which calculated that if EU migration into the UK fell by around 150,000, around about half of the current net total, the impact on tax revenues and benefit expenditure could cost the Exchequer more than £3 billion a year by 2032 and more than £8bn a year by 2057.