Full cost of Brexit put at almost £60bn by UK Government's fiscal watchdog

But it warned the UK could endure an even rougher ride if the road to Brexit was "bumpy," which might force consumers to spend less money or businesses to roll out deeper job cuts.

Philip Hammond, delivering the Autumn Statement, insisted the June 23 vote would “change the course of Britain’s history” but stressed the UK economy remained “resilient”.

However, he admitted the forecast slowdown was due to "lower investment and weaker consumer demand, driven, respectively, by greater uncertainty and by higher inflation resulting from sterling depreciation".

The OBR calculated that by 2020/21 Britain would need to borrow an extra £122bn. Some £58.7bn of this, it said, was directly attributable to the referendum result and the cost of leaving the EU. Around £16bn would be caused by lower immigration.

Balancing the country’s books, which should have happened by 2020, would now take until 2022/23 at the earliest. By the end of the decade the budget deficit was still set to be £20.7bn.

Labour said the Government’s economic statement had placed on record the "abject failure” of the last six years of Tory government and its programme of austerity while the SNP claimed it had revealed a “Brexit bombshell,” that was set to cost Scotland 80,000 jobs and £11.2bn a year.

Mr Hammond announced almost £10 billion in extra infrastructure spending, which means the Scottish Government will receive “very significant additions,” totalling £800 million to spend on capital projects of its choosing.

The Chancellor insisted his mini-Budget “delivers for Scotland," and would involve more discussions on City Deals, including ones for Stirling and the Tay cities, which could result in every city north of the border benefiting from having more powers and freedoms to grow their local economy.

But Derek Mackay, the Scottish Finance Secretary, insisted the additional Treasury cash would only moderate cuts that were already being forced on the Scottish Government's budget.

"Under these plans, Scotland will see a real terms cut to the day-to-day budget that pays for public services. By 2019/20 it is expected to be almost nine per cent lower over the decade; reducing the scope we have to mitigate against Westminster austerity and invest in growing our economy.

"Even on the much-heralded investment in infrastructure, all we have seen is the Chancellor moderating cuts already imposed on Scotland. As a result, Scotland's capital budget will still be around eight per cent lower in real terms across this decade," he added.

In the first major economic assessment following the Brexit vote, the OBR painted a bleak picture, which pointed to:

*lower growth with a loss of 2.4 per cent of GDP over the next five years due to Brexit;

*a short-term boost in trade due to the fall in sterling but over the next decade a slower pace of import and export growth in a “less-trade intensive economy”;

*a rise of almost two per cent in shop prices caused by the post June 23 fall in the pound, peaking at 2.6 per cent in mid-2018;

*lower net migration but not to the “tens of thousands” targeted by the UK Government;

*national debt rising from £1.7 trillion in March to £1.95tr by the end of the decade;

*a rise of 100,000 in unemployment to a UK level of 5.5 per cent and

*a fall in earnings year on year, starting in the second half of 2017.

“It is important to remember that Brexit has not supplanted but has rather increased the main uncertainty already surrounding the outlook for the UK economy, namely, the prospects for productivity growth,” explained the OBR in its report.

Setting out tax and spending plans in his first set-piece economic statement, Mr Hammond said he was striving to ensure the economy was "match fit" for the challenges ahead, unveiling a series of plans aimed at boosting productivity and helping low-income workers.

In a statement largely free of the headline-grabbing surprise announcements deployed by his predecessors George Osborne and Gordon Brown, the Chancellor confirmed an extra £3bn to build more houses, £1.3bn for road improvements to ease congestion in England, more than £1 billion for digital infrastructure and a £2.2bn annual increase by 2020 in research and development to improve innovation and investment.

In a bid to help so-called JAMs, those who are “just about managing,” he announced a modest rise in the so-called National Living Wage, measures to ease cuts to Universal Credit and confirmation that there would be a rise in the tax-free personal allowance to £11,500 next April. There was also a crackdown on letting agent fees, emulating the position in Scotland, and a freeze in fuel duty for the seventh year running.

The most high-profile cash grab was a hike in insurance premium tax, the third in 18 months, on homes, cars and pets. It was branded a “hammer blow for the hard-pressed” by the Association of British Insurers and estimated to cost the typical family an extra £90 a year.

There was a hint that the triple lock on state pensions, which guarantees an annual rise of at least 2.5 per cent, could be under threat after 2020 after MPs were told there would be a review of the controversial policy.

Mr Hammond unveiled a new £23bn "national productivity investment fund" to tackle the UK's "shocking" productivity gap with other countries.

The Chancellor also announced a crackdown on controversial “Rangers-style” tax-free payments.

In March’s Budget the then Chancellor, Mr Osborne, announced plans to target "disguised remuneration schemes" such as Employee Benefit Trusts, a move that could see former Rangers players and staff forced to give up money.

The schemes are similar to those the club used to give employees millions of pounds of tax-free loans. Now 10,000 self-employed workers have been told that they also have until 2019 to repay similar loans or settle up with HM Revenue and Customs.

Confirming that Whitehall spending squeezes would continue, Mr Hammond said plans set out in 2015 would remain in place.

The £3.5bn of efficiency savings announced at the Budget were to be delivered in full but departments which met their targets would be able to reinvest £1bn of efficiency savings in priority areas in 2019/20.

While there was no rabbit pulled from the hat, the Chancellor announced that he intended to switch the date of the main Budget from spring to autumn, beginning next year, so that any tax changes could be announced well in advance of the tax year, which starts in April.

The Treasury denied that the intention to hold two Budgets in 2017 was to facilitate any emergency measures resulting from the triggering of formal Brexit negotiations by the end of March.