Reducing immigration to the tens of thousands could have “catastrophic consequences” for the British economy, according to a new report that derides Theresa May’s policy as “backward looking”.

It comes after the Prime Minister reiterated her commitment to the policy, which has never been met since being introduced by her predecessor David Cameron in 2009, as she published the party’s manifesto for the general election on Thursday.

The report by the new think tank, Global Future, adds that a net migration figure in excess of 200,000 – double the Government’s target – is required to “avoid collapse of whole sectors” and alleviate pressures on the NHS and social care.

It adds: “Our analysis shows that the previous and current Government’s target of cutting net migration to the tens of thousands immediately or in the long-term is based on an outdated and backward looking view of policy in this area. It shows that making substantial cuts in immigration to these levels is not only very difficult but also overwhelming undesirable.

“The UK is close to full employment, has an ageing population and low productivity growth. These factors make immigration an essential ingredient of a successful economy looking ahead.

“Global Future’s top-down economic view is that a net migration figure well in excess of 200,000 will be needed long into the future to avoid catastrophic consequences for the economy.”

Gurnek Bains, the think-tank’s founder, said political leaders have “failed to challenge the assumption that less immigration would be good for Britain” during the election campaign so far.

His report warns that the net number of workers coming from overseas will have to reach an absolute minimum of 200,000 a year in order to sustain economic growth and prevent staff shortages in the NHS.

Mr Bains continued: “It might help particular politicians win elections but voters and our national interests will be the losers.

“Fewer immigrations will bad for Britain’s economy, businesses, finances and public services. There are now political leaders from across the spectrum who either pretend lower immigration will solve every problem or connive in this deceit. These politicians are not only selling voters short – they are selling our country short too.”

UK General Election 2017 Show all 47 1 /47 UK General Election 2017 UK General Election 2017 12 June 2017 British Prime Minister Theresa May leaves 10 Downing Street for the 1922 committee on June 12, 2017 in London, England. British Prime Minister Theresa May held her first cabinet meeting with her re-shuffled team today Getty Images UK General Election 2017 12 June 2017 DUP leader Arlene Foster stands alongside deputy leader Nigel Dodds as they hold a press conference at Stormont Castle as the Stormont assembly power sharing negotiations reconvene following the general election on June 12, 2017 in Belfast, Northern Ireland. Discussions between the DUP and the Conservative party are also continuing in the wake of the UK general election as Prime Minister Theresa May looks to form a government with the help of the Democratic Unionist parties ten Westminster seats. Stormont and the political situation in Northern Ireland has been in limbo following the collapse of the power sharing executive due to the Renewable Heat Incentive scheme scandal which implicated the DUP Getty Images UK General Election 2017 12 June 2017 Priti Patel, International Development Secretary leaves 10 Downing Street Getty Images UK General Election 2017 12 June 2017 Larry the Downing Street cat runs ahead of Michael Fallon Britain's Secretary of State for Defence as he arrives for a cabinet meeting at Downing Street in London, Britain, June 12, 2017. REUTERS/Stefan Wermuth REUTERS UK General Election 2017 12 June 2017 Michael Gove, Environment Secretary leaves 10 Downing Street on June 12, 2017 in London, England. British Prime Minister Theresa May held her first cabinet meeting with her re-shuffled team today Getty Images UK General Election 2017 12 June 2017 Scottish National Party Leader Nicola Sturgeon (C) leaves after speaking to the media in Parliament Square. Getty Images UK General Election 2017 12 June 2017 British Prime Minister Theresa May (C, L) holds the first Cabinet meeting of her new team. Getty UK General Election 2017 11 June 2017 British Prime Minister Theresa May attends church in her constituency with her husband Philip May, a few days after disappointing results in a general election. Rex Features UK General Election 2017 9 June 2017 Leader of the Labour Party Jeremy Corbyn leaves Labour Party HQ this morning, following a general election yesterday. Parliament is hung, with no individual party gaining an overall majority. Post general election reaction. Rex UK General Election 2017 9 June 2017 BELFAST, NORTHERN IRELAND - JUNE 09: DUP leader and Northern Ireland former First Minister Arlene Foster (C) holds a brief press conference with the DUP's newly elected Westminster candidates who stood in the general election Getty Images UK General Election 2017 9 June 2017 A " Get May Out" demo took place opposite the gates of Downing Street, calling for May to resign, after the shock election results and Mays coalition with the DUP. Rex Features UK General Election 2017 9 June 2017 A demonstrator wears a mask depicting Britain's Prime Minister and leader of the Conservative Party Theresa May, poses with a mock gravestone bearing the words "Hard Brexit, RIP", during a protest photocall near the entrance 10 Downing Street in central London AFP/Getty Images UK General Election 2017 9 June 2017 Britain's Prime Minister Theresa May arrives at the Conservative Party's headquarters in London Reuters UK General Election 2017 9 June 2017 Britain's Prime Minister and leader of the Conservative Party Theresa May flanked by her husband Philip delivers a statement outside 10 Downing Street in central Londo Getty UK General Election 2017 9 June 2017 Britain's Prime Minister and leader of the Conservative Party Theresa May leaves Buckingham Palace in London the day after a general election in which the Conservatives lost their majority Getty Images UK General Election 2017 9 June 2017 A TV cameraman watches the door of 10 Downing Street in London Getty Images UK General Election 2017 9 June 2017 Labour leader Jeremy Corbyn is greeted by his Office Director Karie Murphy as he arrives at Labour Party HQ in Westminster, London, after he called on the Prime Minister to resign, saying she should 'go and make way for a government that is truly representative of this country' Dominic Lipinski/PA Wire UK General Election 2017 9 June 2017 Britain's Prime Minister Theresa May arrives at the Conservative Party's headquarters with her husband Philip in London REUTERS/Peter Nicholls UK General Election 2017 9 June 2017 Ukip leader Paul Nuttall speaks during a press conference at Boston West Golf Club where he announced that he is standing down as party leader Joe Giddens/PA UK General Election 2017 9 June 2017 Ruth Davidson, leader of the Scottish Conservatives, leaves the counting centre for Britain's general election with her partner Jen Wilson in Edinburgh, Scotland REUTERS/Russell Cheyne UK General Election 2017 9 June 2017 Scottish Labour leader Kezia Dugdale celebrates with candidate for Edinburgh South Ian Murray as he retains his seat at the Meadowbank Sports Centre counting centre in Edinburgh, Scotland Getty Images UK General Election 2017 9 June 2017 First Minister Nicola Sturgeon speaks to the media at the Emirates Arena in Glasgow, as counting is under way for the General Election Andrew Milligan/PA Wire UK General Election 2017 9 June 2017 Scottish Conservative leader Ruth Davidson at Meadowbank Sports Centre in Edinburgh, as counting is under way for the General Election PA UK General Election 2017 9 June 2017 Scottish National Party (SNP) leader Nicola Sturgeon reacts at the Emirates Arena in Glasgow, Scotland EPA UK General Election 2017 9 June 2017 Jeremy Corbyn, leader of Britain's opposition Labour Party, arrives at the Labour Party's Headquarters in London REUTERS/Marko Djurica UK General Election 2017 9 June 2017 UKIP Leader Paul Nuttall leaves in a car following the vote count for the constituency of Boston and Skegness in Boston, England Anthony Devlin/Getty Images UK General Election 2017 9 June 2017 British Prime Minister and Conservative Party leader Theresa May speaks at the declaration at the election count at the Magnet Leisure Centre in Maidenhead, England. Getty Images UK General Election 2017 8 June 2017 A policer officer enters a polling station in London AP UK General Election 2017 8 June 2017 A woman leaves after casting her vote at the Hove Museum and Art Gallery near Brighton, in southern England Getty UK General Election 2017 8 June 2017 A polling station sign is seen on a telephone box outside the polling station at Rotherwick Hall, west of London Getty UK General Election 2017 7 June 2017 A woman walks past a general election display in the window of a betting shop in Camden on June 7, 2017 in London, United Kingdom. Britain goes to the polls tomorrow, Getty Images UK General Election 2017 7 June 2017 Britain's Prime Minister Theresa May visits Atherley Bowling Club during an election campaign visit on June 7, 2017 in Southampton, England. Britain goes to the polls tomorrow June 8 to vote in a general election. Getty Images UK General Election 2017 6 June 2017 A supporter wears a pair of Jeremy Corbyn decorated tights at a general election campaign event in Birmingham, central England, on June 6, 2017. Britain goes to the polls on June 8 to vote in a general election only days after another deadly terror attack in the nation's captial. AFP/Getty Images UK General Election 2017 6 June 2017 A picture taken in London, shows election leaflets from various parties displayed ahead of the United Kingdom's general elections. Britain goes to the polls on June 8 to vote in a general election only days after another terrorist attack on the nation's capital AFP/Getty Images UK General Election 2017 6 June 2017 Election workers, George Gaunt and Luca Tragid deliver the first ballot boxes, on the Royal Mile in Edinburgh AFP UK General Election 2017 6 June 2017 British Prime Minister Theresa May meets with Conservative party supporters during an election campaign visit to a bakery during an election campaign visit on June 6, 2017 in Fleetwood, north-west England. Britain goes to the polls on June 8 to vote in a general election only days after another terrorist attack on the nation's capital Getty Images UK General Election 2017 5 June 2017 British Prime Minister Theresa May speaks during a general election campaign visit to a removals depot in Edinburgh AFP/Getty Images UK General Election 2017 3 June 2017 Pro-Independence supporters hold a march through Glasgow AFP/Getty Images UK General Election 2017 3 June 2017 Opposition Labour Party leader Jeremy Corbyn campaigns for the upcoming general election in Beeston, Nottinghamshire AFP/Getty Images UK General Election 2017 3 June 2017 Labour leader Jeremy Corbyn reacts to supporters after a rally at Beeston Youth and Community Centre as he visits the East Midlands during the final weekend of the General Election campaign on June 3, 2017 in Nottingham, England. If elected in next week's general election Mr Corbyn is pledging to create a million new jobs and to scrap zero-hours contracts Getty Images UK General Election 2017 1 June 2017 Scottish Conservative and Unionist Party leader Ruth Davidson joins a selection of Scottish Conservative election candidates and activists during campaigning on May 1, 2017 in South Queensferry, Scotland. With only seven days to go until the general election on June 8th, polls are showing the SNP out in front and the Conservatives set to close in on Labour. Getty Images UK General Election 2017 29 May 2017 Prime Minister Theresa May canvasses in Richmond with Conservative candidate Zac Goldsmith on May 29, 2017 in London, United Kingdom. After suffering defeat in the London Mayoral election Zac Goldsmith resigned over the Government's position on Heathrow expansion. He stood as an Independent but lost in a by-election to the Liberal Democrats. Britain goes to the polls on June 8 to elect a new parliament in a general election Getty Images UK General Election 2017 22 May 2017 Liberal Democrat leader Tim Farron poses for a selfie taken by carer April Preston during a General Election campaign visit to the Barlow Medical Centre, in Didsbury, Manchester Yui Mok/PA UK General Election 2017 22 May 2017 Britain's Prime Minister Theresa May speaks at an election campaign event in Wrexham, Wales Reuters UK General Election 2017 22 May 2017 Britain's main opposition Labour Party leader Jeremy Corbyn, and Labour's former deputy Prime Minister, John Prescott, exit the party's general election campaign 'battle' bus as they arrive at an event in Kingston upon Hull, northern England Getty Images UK General Election 2017 22 May 2017 Britain's main opposition Labour Party leader Jeremy Corbyn walks with supporters between venues, before speaking again at another general election campaign event in Kingston upon Hull, northern England Getty Images UK General Election 2017 22 May 2017 An anti-fox hunting protester is taken away and arrested by police outside the venue where Britain's Prime Minister Theresa May was due to launch the Welsh Conservative general election manifesto at Gresford Memorial Hall in the village of Gresford, near Wrexham, North Wales, on May 22, 2017. Britain goes to the polls on June 8 to elect a new parliament in a general election AFP/Getty Images

But it emerged on Thursday that no timetable has been set to achieve the “tens of thousands” pledge and rather it was an “ambition” to bring the number of migrants down. Sir Michael Fallon, the Defence Secretary, told BBC Two’s Newsnight that the economic cost of the policy had not been calculated because there was no fixed deadline.

The Independent and the Open Britain group are running the Drop the Target campaign urging the Government to abandon the “tens of thousands” goal.

If you agree, please sign our petition to call on the Government to Drop The Target: