Reeves has spent two years battering the economy with tax after tax, hammering jobs, pensions, businesses, savings and family farms. She deserves to go. The terrifying thing is that Burnham’s next pick could be even worse. The nightmare scenario is Ed Miliband becoming chancellor and blowing what’s left of the economy to pieces. But even if we dodge that bullet, Burnham has another nightmare lined up for us. Her name is Louise Haigh.

You may dimly remember Haigh. She was Keir Starmer‘s transport secretary before resigning after admitting a fraud offence over falsely reporting a work mobile phone stolen. Incredibly, she’s now emerged as one of Burnham’s key advisers. Even more incredibly, she’s seen as an economic brainbox in Labour circles. Then again, so was Rachel Reeves and look how that turned out. Haigh could be even worse.

Haigh has three deas. As she’s a Labour MP, there are no prizes for guessing what those ideas are. Tax more. Spend more. Borrow more. Instead of producing an original thought, she’s dusted off one of the oldest ideas on the Labour left. She wants capital gains tax (CGT) aligned with income tax. Labour’s Wes Streeting, who should know better, has also suggested it. Both are playing to the Labour Party’s left without considering the consequences.

A big CGT hike would mean that people selling their businesses, investments, second homes, shares or other assets could face dramatically higher tax bills. Haigh insists it would shift the burden away from work and onto what she calls “unproductive capital accumulation”. She’s obviously never spoken to someone who’s set up their own business. Supporters claim her plan could raise £14billion a year. There’s just one awkward problem.

HMRC‘s own analysis found the exact opposite. It concluded that increasing capital gains tax by 10 percentage points could actually cost the Treasury up to £3.7billion in lost revenue. Which will surprise absolutely nobody who understands how CGT works.

CGT is simple to avoid. If you hold an asset, don’t sell it. Alternatively, move overseas before cashing in. Hold the asset until death and the CGT bill disappears (although you might pay inheritance tax). Even Haigh has spotted the flaw in her plan, and has floated an even worse solution. Which is to punish anybody who tries to leave Britain by hitting them with an exit tax. That would be sheer economic madness.

Who would build a business here knowing they couldn’t leave the country without HMRC picking their pockets? Why would overseas investors bring money to Britain if getting it out again became almost impossible? Foreign investment is already drying up under Reeves. Haigh’s answer is to frighten away whatever’s left.

Former Labour PM Tony Blair has savaged the plan and urged Burnham to bin it, saying “Britain cannot tax our way to prosperity”. Tory leader Kemi Badenoch warns it will “completely crush investment in this country”. But Haigh just ploughs on, with the airy confidence of somebody who doesn’t understand what she’s doing.

Incredibly, Haigh wants to go even further. As well as an exit tax, she wants to impose CGT on assets at death. That’s on top of any inheritance tax bill. This smash-the-rich nonsense may sound clever in a leftie think tank seminar but would wreak havoc in the real world. Entrepreneurs won’t invest. Wealth creators will leave. Tax revenues will shrink. Britain will become poorer. And the spending splurge Haigh dreams about will become even less affordable.

So this is the economic powerhouse advising Burnham. Worse still, he’s reportedly considering her for chief secretary to the Treasury.

The most left-wing government in modern British history is about to be replaced by an even more left-wing one. With Haigh pulling the economic strings, we could soon find ourselves begging for Rachel Reeves to come back.