THE biggest fault line in the General Election has just appeared, thanks to some deeply revealing leaks from Rishi Sunak’s office and a hastily arranged speech yesterday in which the Tory leader “cut the green crap”, as ex-PM David Cameron once put it, and abandoned key pledges in the move to net zero.

Today it’s Humza Yousaf’s turn.

Will he use First Minister’s Questions to keep Scotland on a fast track to green change? And maybe more importantly, will he kickstart a campaign to make sure the Scottish public are with him?

Sunak seemed to surprise most of the media north of the Border (except the valiant National) by announcing the ban on new petrol and diesel car sales will slip from 2030 to 2035 … phasing out 80% of new gas boilers will slip to 2035 along with the 2026 ban on off-grid oil boilers.

There will be no new energy efficiency rules for landlords or homeowners, no new taxes to discourage flying, no policies to encourage carpooling and long-delayed recycling schemes have been ruled out.

Now I’ll grant you, delaying the petrol car ban by five years doesn’t look cataclysmic. And householders may feel relief at not facing immediate bills for heat pump installation.

Even though – as they column will never stop arguing – the solution for Scotland and the UK is not individual heat pumps but massive, coordinated state-led investment in collective district heating so we finally catch up with the fairer, more efficient way northern Europe has heated homes for a century.

READ MORE: 'Irrelevant' if Alister Jack laid Section 35 order over policy dispute

But to anyone casting their ear across the PM’s speech, Sunak may have sounded like sweet reason, rescuing the public from “daft ideas” like seven recycling bins, (even though they’ve never been formally proposed by anyone.)

Equally, it was a bit of a nerve for the PM to complain about green decisions lacking scrutiny (just 17 minutes to debate the carbon budget) but he then announced a raft of big changes to government policy while Parliament is on (checks diary) recess. Something that prompted an infuriated Speaker of the Commons, Lindsay Hoyle to comment: “If he had the power, the speaker would recall the House immediately ... This is not the way to do business.”

Quite.

But all that aside, was the announcement really that bad? Yes, it really was.

Listen to his own side digest the net zero climbdown.

Former energy minister Chris Skidmore (in New York for “climate week”) warned Sunak he was making the “greatest mistake of his premiership”, and the Tory backbencher wouldn’t rule out a letter of no confidence to trigger a leadership challenge.

The National: Prime Minister Rishi Sunak has weakened a host of net zero pledges (Justin Tallis/PA)

Former climate minister Zac Goldsmith has called for a General Election immediately.

Tory grandee, Alok Sharma (President of COP26) who managed to overturn England’s decade-long onshore wind farm veto last week was horrified. “If we have countries around the world resiling from their commitments, the Earth is going to be on life support,” he said.

Of course, green Tory rebels are not known for their political cunning, personal daring or general support within a party ready to put manky brown water between itself and a Labour Party that’s already pledged to reverse everything Sunak has announced if they win next time.

But it’s not just angry Tories, Sunak should worry about.

On the international stage, former US vice president Al Gore says Rishi Sunak’s move to amend net zero targets is “unfortunate” and “doing the wrong thing”.

International green think tank E3G predicts the move will drive up energy bills and “the economic damage to the UK could be catastrophic”. The Energy and Climate Intelligence Unit say the “sheer number of U-turns speaks of chaos at the heart of government” and former Department of Energy strategy chief Adam Bell predicts the move will go “straight to judicial review” because legally binding carbon targets cannot now be met.

The founder of FairChange, which promotes electric vehicles, says the change could risk “billions in investment and thousands of jobs” and Ford UK Chair Lisa Brankin has put the boot in a good deal further.

READ MORE: Rishi Sunak delays ban on sale of new petrol and diesel vehicles

“Our business needs three things from the UK Government: ambition, commitment and consistency. A relaxation of 2030 [for the ban on new petrol and diesel car sales] would undermine all three.”

Ouch.

Sunak's net zero climbdown hasn’t just infuriated green campaigners, it’s done the impossible and created common cause between activists and big business. Why? Because business likes certainty, and thanks to constant backtracking from helicopter-loving Rishi, there’s absolutely no certainty about energy policy in Britain.

It’s net zero one day and new coal mines the next. Backing for electric car battery production in one speech and a delay to banning petrol engines the next. News that no offshore wind projects have won government contracts one week and boasting about the size of existing installations the next.

To anyone in the know, to business, investors and the money men and women – the British Government is now a busted flush and there are plenty other places to take green cash.

If Scotland was independent right now, we’d be hoovering it up. But energy is a reserved issue and while we’re part of this increasingly un-investable Union, Scotland is tarred with the same untrustworthy brush.

Compare and contrast with Denmark whose pro-renewables stance has endured half a century since the OPEC oil crisis – weathering dozens of changes in government. That’s consistency. And that’s where green investors will go.

READ MORE: Scottish Child Payment impact 'biggest since fall of Berlin Wall'

It’s tragic and one of the biggest reasons we need independence. But that argument doesn’t make itself.

Green MP Caroline Lucas, SNP leader Stephen Flynn and Labour’s Energy Spokesperson Ed Miliband were all quick to express their outrage over Sunak’s U-turn.

Yet the Scottish media ignored well-sourced leaks until the Tory leader’s unexpected speech confirmed this important change of direction – happier to snipe about the Rutherglen by-election, Fergus Ewing’s possible suspension, a legal challenge for Glasgow’s low emissions zone and the Edinburgh trams report.

All important, but hardly bigger than Sunak’s unmistakeable signal that the UK is not open for green business. And that is now the only sustainable kind.

Politicians, papers and pressure groups down south are preparing to go to war over this – so the question for Scotland is simple and urgent.

The National: The First Minister is in New York City this week (Robert Perry/PA)

Will Humza Yousaf lead the fight or leave it to Labour and go-ahead Wales? Might he water down Scotland’s green objectives to match London’s monumental back-slide?

At First Minister’s Questions today, the FM must seize the initiative and nail his colours firmly to the green mast.

But if Scotland’s more ambitious targets remain intact – as you’d expect from an SNP/Green coalition government – another vital question needs answering. How will the Scottish Government take the Scottish public with them?

READ MORE: Lorraine Kelly left 'uncomfortable' at old clip with Russell Brand

It’s all very well pointing to pollsters like YouGov who found 71% support net zero by 2050.

But the same company found few would make “substantial” changes to their lifestyle and many said the cost-of-living crisis should be a bigger priority.

Green is popular, and the urgency of action is understood – particularly by younger generations. But individual green measures still get pelters – because they’re new, sometimes flawed, often demand individual taxpayer not collective state investment and generally because their need is not explained with sufficient urgency, coherence or passion within a wider, Scottish Government strategy.

If Rishi can use TV to focus scrutiny on his shabby net zero plans, Humza can do the same to explain while we will stay on the straight and narrow.

Scotland and the cause of independence need a stronger, more emphatic, urgent and better argued response to the UK’s sudden green climbdown that more low key business as usual at Holyrood.