Jeremy Corbyn has unveiled leaked government documents that appear to show Boris Johnson misled the public over the nature of his new Brexit deal with the EU.

Labour says the internal Treasury paper, marked “official sensitive”, warns of new customs checks between Britain and Northern Ireland after Brexit – which the prime minister has claimed would not exist.

Speaking in central London on Friday, Mr Corbyn told journalists: “Today I can reveal further hard evidence that Johnson is deliberately misleading the people”.

He added: “This document is very ominous. There will be other secret reports like this one in every government department that reveal the disastrous impacts of his policies on the safety of the food you eat, on the rights you have at work, on the pollution of the air that we breathe and on the jobs and industries that people work in.

“These reports exist but the government is hiding them from you because in this election the Conservatives want you to vote blind.”

General election: On the campaign trail Show all 114 1 /114 General election: On the campaign trail General election: On the campaign trail Boris Johnson drives a Union flag-themed JCB, with the words "Get Brexit Done" inside the digger bucket, through a fake wall emblazoned with the word "GRIDLOCK", during a general election campaign event at JCB construction company in Uttoxeter, Staffordshire AFP via Getty General election: On the campaign trail A sculpture of an owl is bedecked with an EU beret as Liberal Democrat leader Jo Swinson gestures during an interview at a general election campaign event in Bath AFP via Getty General election: On the campaign trail Boris Johnson (C) talks during a question and answer session on a general election campaign visit to Ferguson's Transport in the town of Washington, west of Sunderland AFP/Getty General election: On the campaign trail Boris Johnson tries to save a shot during a warm up before a girls football match while on the campaign trail in Cheadle Hulme, northwest England POOL/AFP via Getty General election: On the campaign trail Jeremy Corbyn makes cup of coffee as he campaigns in Barry, south Wales AFP General election: On the campaign trail Nicola Sturgeon poses as she launches the SNP campaign bus tour, at Queensferry Crossing in Edinburgh, Scotland AFP via Getty General election: On the campaign trail Boris Johnson reacts as he changes a wheel of a Formula One car during a Conservative Party general election campaign visit to Red Bull Racing in Milton Keynes POOL/AFP via Getty General election: On the campaign trail Britain's Prime Minister Boris Johnson visits a Christmas market in Salisbury REUTERS General election: On the campaign trail Liberal Democrat Leader Jo Swinson on the election campaign bus on route to Chelmsford PA General election: On the campaign trail Labour leader Jeremy Corbyn talking to a university worker outside Birkbeck/SOAS University of London, at the announcement of his parties of the plan for the extension of workers' rights PA General election: On the campaign trail Nicola Sturgeon plays a game with string during a visit to Perth and District YMCA Getty Images General election: On the campaign trail Brexit Party leader Nigel Farage picks up a copy of The Brexiteer during a visit to JPI Printers in Dinnington PA General election: On the campaign trail Boris Johnson, centre, talks to veteran James Gammer as he visits a veterans centre AP General election: On the campaign trail SNP supporters meet First Minister Nicola Sturgeon following her address during a St Andrews day election speech Getty General election: On the campaign trail Jeremy Corbyn has a photo taken outside Birkbeck/SOAS University PA General election: On the campaign trail Liberal Democrat leader Jo Swinson during a visit to the Cardiff United Synagogue PA General election: On the campaign trail Brexit Party leader Nigel Farage reacts as he attends an election debate ITV/Reuters General election: On the campaign trail Jeremy Corbyn wears a jacked displaying Labour's slogan 'For the many, not the few' EPA General election: On the campaign trail Prime Minister Boris Johnson on The Andrew Marr Show Getty General election: On the campaign trail Nicola Sturgeon plays with local children during a visit to the Jelly Tots & Cookies Play Cafe in Uddingston, South Lanarkshire PA General election: On the campaign trail Opposition Labour Party leader Jeremy Corbyn eats some chips in Whitby, northern England AFP via Getty General election: On the campaign trail Boris Johnson and Conservative MP George Eustice, left, tour 'Rodda's Clotted Cream' whilst campaigning in Cornwall Getty General election: On the campaign trail Jo Swinson during a visit to Dunkertons Cider Company, an organic and plastic free brewery in Cheltenham PA General election: On the campaign trail Jeremy Corbyn holds up unreacted documents with NHS staff. Mr Corbyn released uncensored official documents which he says provides confirmation that the NHS is on the table in trade talks with the USA EPA General election: On the campaign trail Nigel Farage meets locals in Barnsley market PA General election: On the campaign trail Nicola Sturgeon launches the SNP's general election manifesto Getty General election: On the campaign trail Labour Party leader Jeremy Corbyn addresses the audience during the launch of Labour's environmental policy in Southampton Getty General election: On the campaign trail Boris Johnson tries an apple as he visits Healey's Cornish Cyder Farm in Callestick AP General election: On the campaign trail Jo Swinson helps make a chicken tikka masala during a visit to the Ashoka restaurant in Bearsden, Glasgow PA General election: On the campaign trail Nigel Farage playing golf on a range at One Stop Golf in Hull PA General election: On the campaign trail Jeremy Corbyn addresses the audience during a climate emergency rally in Falmouth Getty General election: On the campaign trail Liberal Democrat leader Jo Swinson meets supporters during a visit to Dunkertons Cider Company PA General election: On the campaign trail Boris Johnson visits Chulmleigh College AP General election: On the campaign trail Labour Party leader Jeremy Corbyn as he appearing on the BBC political programme The Andrew Neil Show. The opposition leader defended his handling of anti-Semitism allegations after Britain's most senior rabbi suggested the issue was a "new poison" within the party that had been "sanctioned from the very top". In an unprecedented intervention ahead of next month's election, Chief Rabbi Ephraim Mirvis suggested Corbyn was "unfit for high office" due to his perceived failure to clamp down on the problem within the party BBC/AFP via Getty General election: On the campaign trail Liberal Democrat leader Jo Swinson alongside Julian Dunkerton, whose father founded and ran Dunkertons Organic Cider, during a visit to the company's organic and plastic free brewery in Cheltenham, Gloucestershire, whilst campaigning for the General Election. PA Photo. Picture date: Tuesday November 26, 2019. See PA story POLITICS Election. Photo credit should read: Aaron Chown/PA Wire Aaron Chown PA General election: On the campaign trail Prime Minister Boris Johnson launches the Conservative Party Scottish Manifesto in North Queensferry Getty General election: On the campaign trail Britain's Opposition leader Jeremy Corbyn poses with WASPI (Women Against State Pension Inequality) supporters after he outlined Labour's plans to repay the "historical debt of honour" owed to women born in the 1950's AFP via Getty General election: On the campaign trail Jo Swinson alongside the Lib Dem's candidate for Truro and Falmouth, Ruth Gripper, and founder of Finisterre, Tom Kay, during a tour of the British surfing brand, which creates sustainable surfing gear, in St Agnes, Cornwall PA General election: On the campaign trail Prime Minister Boris Johnson poses with sheep as he visits the Royal Welsh Showground, in Llanelwedd PA General election: On the campaign trail A coalition of NHS (National Health Service) campaigners led by "Keep Our NHS Public" and "We Own It", pose for photographs with masks of US President Donal Trump, right, and Prime Minister Boris Johnson carving up the NHS with a giant knife and fork, as they take part in a demonstration on Parliament Square. 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Photo credit should read: Stefan Rousseau/PA Wire Stefan Rousseau PA General election: On the campaign trail Liberal Democrat leader Jo Swinson (left) during a visit to the Gurdwara Singh Sabha Temple in Glasgow PA General election: On the campaign trail Labour leader Jeremy Corbyn meets Colin and his mother after a speech at the University of Lancaster Getty Images General election: On the campaign trail Britain's Green Party co-leaders Jonathan Bartley, Sian Berry, and deputy leader Amelia Womack, wave during the launch of the party manifesto at the Observatory at London Wetland Centre Reuters General election: On the campaign trail Scottish Nationalist Party leader Nicola Sturgeon meets voters and activists at Cafe Roma in Clarkston, Glasgow AFP via Getty General election: On the campaign trail Protestors participate in an anti-Boris Johnson rally in his constituency Uxbridge, west London AFP via Getty Images General election: On the campaign trail Brexit Party leader Nigel Farage 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The leaked document, entitled “NI Protocol: Unfettered access to the UK internal market”, appears to be an official analysis of the Northern Ireland protocol, which replaces the Irish border backstop negotiated by Theresa May.

The Labour leader said the confidential report “drives a coach and horses” through Mr Johnson’s promise to the DUP that there will be no border in the Irish Sea under his Brexit plan.

The paper, which has been seen by The Independent, reveals there would be customs declarations and regulatory checks on goods travelling between Northern Ireland and Britain – which Mr Johnson has repeatedly denied.

Checks could be “highly disruptive” to the Northern Ireland economy, where 98 per cent of exporters to Britain are small businesses who will be hit hard by these extra costs, according to the report.

Prices of imported high street goods are likely to rise, which would hit business profits and the retail sector, it added.

Mr Corbyn said: “It is there in black and white. It says there will be customs declarations, absolutely clearly, for trade going from Northern Ireland to Great Britain.

“The government cannot rule out regulatory checks, rules of origin checks and animal and public health checks also. For trade going the other way, from Great Britain to Northern Ireland, there will be all of the above plus potentially damaging tariffs.”

The leaked document seems to confirm in the government’s own words what essentially all trade experts say about the Brexit deal with regard to customs, but which Mr Johnson has continued to deny point-blank when asked in public.

At the start of the election campaign, the prime minister was asked in person by Northern Ireland business leaders whether they would be subject to customs declarations.

“You will absolutely not,” he told them. “If anyone asks you to do that tell them to ring up the prime minister and I’ll direct them to put that form in the bin.”

However, Steve Barclay, the Brexit secretary, and Julian Smith, the Northern Ireland secretary, have both previously said that some checks will be necessary on goods travelling across the Irish Sea.

Mr Johnson was challenged over the disparity between the document and his previous claims during a campaign visit in southern England, where a journalist asked him: “Either you don’t know the detail of your policy or you are lying. Which is it?”

He replied: “I know perfectly well that goods going from NI to GB and GB to NI will have no checks. The only checks will be those going via NI into Ireland. Everybody understands that and that’s so we avoid a hard border between Ireland and Northern Ireland.”

Asked what voters should believe, the prime minister said: “They should believe exactly what I say, which is that there will be no checks on goods going from GB to NI or NI to GB, because we are going to come out of the EU whole and entire.

“That’s the objective we secured, which is a vast improvement on the original proposal, which would indeed have carved out Northern Ireland and kept it in the EU for all sorts of purposes.”

Earlier in the campaign, Labour presented separate leaked documents that showed UK negotiators have been repeatedly discussing the NHS with US trade officials, despite claims by Mr Johnson that the NHS is not “on the table” in talks.