Business leaders today urge the Chancellor to unveil billions of pounds worth of public investment next month in the wake of the Brexit result.

The CBI also calls on Theresa May’s government to push ahead with large-scale infrastructure projects, including dualling the A1 from Scotland to Newcastle.

The organisation warns that the UK faces an “uncertain economic outlook” following the vote to leave the European Union and says that there had rarely been a more important Autumn Statement, the yearly event seen as a mini-Budget.

Read more: Nicola Sturgeon's post-Brexit blueprint for EU deal to be published by end of 2016

Earlier this week the CBI welcomed the decision to build a third runway at Heathrow, a move the Scottish Government estimates could create an extra 16,000 jobs in Scotland.

But it warns that ministers have to do much more to create business confidence and encourage industry to invest in the UK.

Among its demands is a call for an average annual increase of £6 billion in public investment.

Carolyn Fairbairn, the CBI director-general, called on the Chancellor to set out a “pro-enterprise agenda that instils confidence and kick-starts investment."

She warned: “With huge variations in productivity between different parts of the country, the top priority must be to set out a programme that will get our regions firing on all cylinders and supports businesses to innovate, invest and create jobs in the years ahead.”

It was time to “incentivise businesses to invest today, rather than postpone until tomorrow,” she warned.

The CBI believes that with interest rates at rock bottom now is the time to improve infrastructure.

Read more: Nicola Sturgeon's post-Brexit blueprint for EU deal to be published by end of 2016

Economists have warned that the UK could be headed for a combination of an economic slowdown coupled with rising inflation, after the value of the pound plunged in the wake of the Brexit result.

The Chancellor Philip Hammond was warned earlier this week that the fall in the value of Sterling means that he faces an £84 billion “black hole” in next month’s Autumn Statement.

Yesterday Mrs May also faced accusations that she was ignoring her own "dire warnings" about the consequences of a so-called hard Brexit, after a secret recording emerged of her setting out her fears for the economy a month before the EU referendum.

The Conservative leader told investment bankers in May that she was concerned businesses would have to leave the UK if Britain quit the EU.

In recent weeks, however, she has argued that the UK's freedom to trade in the EU Single Market should not come at the expense of immigration controls.

Mrs May, who was Home Secretary at the time, was recorded saying: "If we were not in Europe, I think there would be firms and companies who would be looking to say, do they need to develop a mainland Europe presence rather than a UK presence? So I think there are definite benefits for us in economic terms."

Andrew Gwynne, shadow minister without portfolio, said: "As if we needed it, this recording is cast-iron evidence of how Theresa May and other senior Tories have been saying one thing in private about the economic impact of Brexit, and another in the comfort of Tory conference halls.

Read more: Nicola Sturgeon's post-Brexit blueprint for EU deal to be published by end of 2016

"It's plain that she recognises what a disaster it would be for Britain to lose access to the Single Market, so why doesn't she be honest with the British people and say how she plans to retain it?"

Liberal Democrat leader Tim Farron said: "It is disappointing that Theresa May lacked the political courage to warn the British public as she did a group of bankers in private about the devastating economic effects of Brexit.

"But far more disappointing is that now she is supposedly in charge, she is blithely ignoring her own dire warnings and is prepared to inflict an act of monumental self-harm on the UK economy by pulling Britain out of the Single Market."

The SNP's economy spokesman Stewart Hosie accused the UK Government for failing to provide an economic strategy after years of a “failed austerity agenda”.

Downing Street said that the Prime Minister had made similar comments during the EU campaign.

Meanwhile, in a speech later today John McDonnell, Labour’s shadow chancellor, will warn that Brexit will turn the UK into the Singapore of the north Atlantic, with low taxes for select groups.