Jeremy Corbyn has not ruled out backing the Brexit deal Theresa May secures with Brussels, as he rounded off a Labour conference dominated by Europe.
The Labour leader called on the prime minister to ditch her Chequers blueprint for Britain's European exit in favour of a "sensible" deal that includes a customs union with the EU to prevent a hard border in Northern Ireland and protects workers' rights and environmental standards.
If not, Mr Corbyn said Mrs May needed to "make way for a party that can".
He told Labour's annual gathering in Liverpool that a "no-deal" Brexit would be a "national disaster" and his preference in the first instance was for a general election.
"Failing that, all options are on the table," he said.
A senior Labour source insisted the party were sticking to their six tests for a Brexit deal, but said Mr Corbyn was "reaching out to create political space" for the PM to agree a Brexit deal.
It comes after a conference dominated by debate on Labour's "constructive ambiguity" on Brexit, with the party not ruling out support for a second referendum but also pledging to respect the 2016 Leave vote.
In an hour-long speech to a packed hall, Mr Corbyn pledged a "green jobs revolution" and an expansion of free childcare.
He also denounced "greed-is-good capitalism", which he said was holding the UK economy back.
"People in this country know - they showed that in June last year [at the general election] - that the old way of running things isn't working anymore," he said.
"That's why Labour is offering a radical plan to rebuild and transform Britain."
He accused the "political and corporate establishment" of propping up the financial system which caused millions of people misery in the wake of the 2008 financial crash.
Seeking to sketch out details of how Labour would try to change what he sees as a broken system, Mr Corbyn pledged to:
:: Work with industry and unions to create 400,000 "green jobs" by 2030, with investment focused on offshore and onshore wind, solar energy and home energy efficiency
:: Set an ambitious target to reduce net carbon emissions by 60% by 2030 and to zero by 2050
:: An extension of free childcare
:: Give workers seats on company boards and set up employee shareholding funds
:: End what he called the "racket" of privatisation and outsourcing
:: Bring in a tax on second homes to fund an ambitious house-building programme
:: Oversee a foreign policy with "progressive values and international solidarity" at its heart, with no more "reckless wars, like Iraq or Libya"
:: Recognise a Palestinian state upon entering Downing Street
"We can no longer tolerate a set-up where the real economy, in which millions work, is just a sort of sideshow for the City of London and for banks fixated on piling up profits around the world," he told the conference.
"Inequality is not just a matter of incomes. It's about having a real say too.
"That's why we are not only determined to rebuild our economy, communities and public services, but also to democratise them, and change the way our economic system is run in the interests of the majority."
He tried to draw a line under the party's antisemitism row, promising to "eradicate" it "both from our party and wider society" and telling the Jewish community: "We are your ally."
But Mr Corbyn said he would not shy away from criticising Israel, hitting out at illegal settlements and the detention of Palestinian children as an "outrage".
The Labour leader said his party was "ready to take charge" and deliver "a real alternative to the people of Britain - a radical plan to rebuild and transform our country".
He declared Labour represents "the new political mainstream" and offers voters "an alternative to the politics of austerity, of social division and of international conflict".
And he won a standing ovation as he promised: "Where the Tories have divided and ruled, we will unite and govern.
"We represent the new common sense of our time. And we are ready to deliver on it."
But the Conservatives said Mr Corbyn had demonstrated "at every turn he is unfit to govern".
Tory party chair Brandon Lewis said: "All he offers are failed ideas that didn't work in the past and would leave working families paying the price with higher taxes, more debt and more waste - just like last time."
Mr Lewis said Labour's Brexit stance would take Britain "back to square one" and added: "Only the Conservatives offer people opportunity for the future."
The Confederation of British Industry said it agreed with much of Mr Corbyn's vision, but said "this will only happen if Labour invites business into the tent".
Director-general Carolyn Fairbairn said: "Continual public barbs and backward-facing policy are deterring entrepreneurs and investors, at a time when we need them most.
"Policy built collaboratively will help build a fair, progressive and pro-enterprise Britain. Policy built on ideology and diktat will do the opposite."