City has been too quick to dismiss the threat of Jeremy Corbyn

Parliamentary Business: It's difficult to read his manifesto and believe it will not resonate with millions of households

Jeremy Corbyn has raised £46,000 for his Labour leadership campaign – which, at an average donation of £22.62, means more than 2,000 donations.

I wonder how many of those people had heard him speak before June, or could have at least picked his voice out from a crowd; more so the tens of thousands of Labour supporters who want to install the veteran left-winger as Ed Miliband’s permanent successor.

On 8 May, as the extent of Labour’s election defeat became clear, Mr Corbyn’s name did not appear on Paddy Power’s list of more than 30 likely next Labour leaders. To put that into context, Douglas Alexander, who had been defeated by 20-year-old Mhairi Black as part of the SNP’s near clean sweep in Scotland, was quoted at 25-1; the odds stretched as far as 100-1 for the Wirral South MP Alison McGovern.

After 32 years in Parliament, and a maiden speech that thundered against the destruction of the now long-gone Greater London Council, Mr Corbyn is an overnight success. Paddy Power now has Jeremy Corbyn at 9-4, second favourite only to the shadow Health Secretary Andy Burnham; an increasing number of polls tell us he is actually in the lead, and there is little indication he is losing momentum.

“So what?” the City is thinking. The Conservatives have a five-year fixed-term and Mr Corbyn will surely be unelectable come 2020.

Even before then, Labour MPs would probably orchestrate a coup. If that fails, rumours persist that Mr Corbyn would stand down after a couple of years to allow the emergence of a more electable, softer left figure, such as the impressive shadow civil society spokeswoman Lisa Nandy.

The risk for the left, then, of course, is that a more mainstream figure, such as shadow Communities Secretary Emma Reynolds, will have also come to the fore, just in time to rescue Labour from itself ahead of the election.

However you cut it, it’s easy for City executives to look at Mr Corbyn as posing little threat to their future wealth.

But what if this isn’t some passing dalliance, an ageing Labour membership rejoicing in the sepia-tinged memory of youthful radicalism? Surely, the condescending way that Mr Corbyn’s campaign has been underestimated by many has only added to its strength?

What’s more, as Labour leader he would probably regain many of the working class Labour voters who have defected to Ukip, given that it seems clear he will argue for an exit in the European Union in/out referendum. An anti-austerity message is also likely to grow more powerful if wages, and living standards, fail to grow at the pace of the wider economy – part of the SNP’s election success can be attributed to this feeling in Scotland.

It’s difficult to see Mr Corbyn as a future PM, but, unlike two months ago, it’s not an impossibility. Big business would do well to take a look at Mr Corbyn’s largely ignored, eight-page economic manifesto, published last week.

This starts off in fairly neutral terms – “wealth creation is a good thing: we all want greater prosperity”– before going on the attack. “If you believe the Conservative myth, then wealth creation is solely due to the dynamic risk-taking of private equity funds, entrepreneurs or billionaires bringing their investment to UK shores.”

Cutting corporation tax to 18 per cent comes under fire, given that it was already the lowest in the G7 at 20 per cent and fully half the US rate of 40 per cent. Mr Corbyn complains that this “political choice will see our revenue intake from big business fall by £2.5bn in 2020”.

Referring to TUC figures, he notes “the longest period of falling real wages since the 19th century”, arguing that “the average household is still awaiting recovery”. The Northern Powerhouse, he surmises, is “largely southern hot air”, and he wants the Bank of England to be given a mandate to invest in large-scale housing and other infrastructure projects.

Mr Corbyn proposes introducing “proper” anti-avoidance into UK tax law and increasing staff numbers at HMRC and Companies House to make sure big businesses aren’t channelling taxable profits to other countries. He also notes the flaws in George Osborne’s new national living wage, but points out that it did “outflank the too-modest-by-far” Labour plan to raise the minimum wage to only £8 an hour over five years.

This economic manifesto is clearly to the left of Mr Miliband. Mainstream Labour MPs shake their heads in agreement that it is symptomatic of the electoral disaster that would face them under Mr Corbyn in 2020.

Clearly, it is an attack on the City, or at least the existing way it operates, that would truly test the resilience of the UK as a major financial services centre. Renationalisation is left unmentioned in this document, but its spectre looms over every sentence – major corporations would surely flee the UK for more loosely regulated emerging economies.

But it’s difficult to read the manifesto and believe it will not resonate with millions of households across the UK.

Mr Corbyn might not ever hold the keys to Number 10, but if he secures the Labour leadership next month, he must be considered a political risk to British business. And that’s a role, you would figure, that Mr Corbyn and his supporters would relish.

Twitter.com/@mleftly