Jeremy Corbyn will go into the General Election pledging to nationalise key industries and reverse years of austerity, according to a leaked draft of the Labour manifesto.
The 43-page document sets out plans to take the energy industry, railways, buses and the Royal Mail back under public control.
It commits Labour to scrapping tuition fees, boosting workers' rights and reversing a series of benefits cuts - including the so-called bedroom tax.
Labour is expected to finalise its manifesto at a meeting on Thursday, but an extraordinary leak of the policy document saw details released a week ahead of its planned publication in a blow to the party's campaign strategy.
The Daily Mirror and Daily Telegraph both claimed to have obtained drafts of the manifesto ahead of the meeting.
According to the Mirror:
:: Railways will be renationalised as each private franchise expires, with fares frozen and guards put back on driver-only trains
:: Publicly owned bus companies will be established
:: Royal Mail will be returned to public ownership following the coalition government's "historic mistake" of selling it off
:: The manifesto commits to "take energy back into public ownership" by setting up a rival to the existing Big Six private firms
To pay for the policy pledges, Labour has already announced plans to hike corporation tax to 26% by 2022, bringing in an extra £20 billion for the Exchequer, and indicated that people earning more than £80,000 will face tax rises.
But the manifesto indicates a further levy on firms "with high numbers of staff on very high pay".
Labour has insisted its manifesto will be fully costed, and the document vows to eliminate the deficit and balance the budget by the end of the next parliament, the Mirror reported.
Mr Corbyn's effort to win support from voters who backed Brexit may be hampered by the manifesto's measures on the EU and immigration.
The Telegraph said the document ruled out setting a target for cutting net migration - something Theresa May has committed to despite so far failing to hit the Conservatives' "tens of thousands" ambition.
The manifesto says Labour believes in "fair rules and reasonable management" of migration but rules out "making false promises on immigration numbers".
Mr Corbyn has insisted "Britain is leaving the European Union" but the manifesto reportedly rules out breaking away from Brussels without a deal.
The Labour leader has highlighted the importance of tackling the housing crisis, and the draft document commits councils to build 100,000 new homes, while private landlords will only be allowed to raise rents in line with inflation.
In an effort to bridge party divides over Trident, the manifesto commits Labour to the nuclear deterrent, but in a nod to Mr Corbyn's opposition to the weapons it says "any prime minister should be extremely cautious about ordering the use of weapons of mass destruction which would result in the indiscriminate killing of millions of innocent civilians".
A spokesman for Mr Corbyn said: "We do not comment on leaks. We will announce our policies in our manifesto, which is our plan to transform Britain for the many, not the few."
The final version of the pitch to voters will be have to be approved by around 80 Labour figures, a senior party source said, including the shadow cabinet, the national executive committee, the parliamentary committee of the Parliamentary Labour Party, Welsh and Scottish Labour leaders, members of the national policy forum and trade union representatives.
The meeting in London is also expected to help define the "attitude" of the party to issues in the election that will not be covered by the manifesto, according to the Labour Party rulebook.
A Conservative spokesman said: "This is a total shambles. Jeremy Corbyn's plans to unleash chaos on Britain have been revealed.
"The commitments in this dossier will rack up tens of billions of extra borrowing for our families and will put Brexit negotiations at risk. Jobs will be lost, families will be hit and our economic security damaged for a generation if Jeremy Corbyn and the coalition of chaos are ever let anywhere near the keys to Downing Street."
The Prime Minister sought to put pressure on Labour over defence policy by committing to inflation-busting increases in spending.
Mrs May said she will "always put Britain's national security first" as she renewed the Tory pledge to spend 2% of national income on the defence budget.
Her focus on security came as The Times reported a rift over tax policy between Mrs May and Chancellor Philip Hammond.
The newspaper said Mrs May's team was infuriated after Mr Hammond effectively committed the Prime Minister to ditching the Tory promise not to raise VAT, income tax or national insurance.
A Tory source dismissed the rumours of a rift as "little more than incorrect Westminster tittle-tattle".
Meanwhile, Liberal Democrat leader Tim Farron is campaigning in Wales, voicing his support for the Swansea Bay tidal lagoon project.
Thursday also marks the deadline for nominations ahead of the June 8 contest. Would-be MPs must submit their nomination papers - and a £500 deposit - to their constituency's returning officer by 4pm.