BORIS Johnson today makes clear that he will never debate Nicola Sturgeon and will never agree to facilitate a second Scottish independence referendum as long as he is in Downing St.

The clear rebuff to the First Minister came as the High Court in London threw out a challenge to ITV from the SNP and Liberal Democrats against the broadcaster's decision to exclude their party leaders from a televised election debate tonight, which will only feature the Prime Minister and Jeremy Corbyn.

HeraldScotland: Camley's cartoon: SNP's TV debate challenge thrown outCamley's cartoon: SNP's TV debate challenge thrown out

The ruling will almost certainly mean the BBC TV head-to-head a week before polling day will also feature just the two main party leaders.

READ MORE: Professor John Curtice: It would take 'little' for Scotland to be transformed'

As a result, there is now set to be no opportunity for Ms Sturgeon and Mr Johnson to challenge each other in person before voters.

The judges ruled that the format of the debates was a matter of "editorial judgement" and there was "no arguable breach of the Broadcasting Code".

Ian Blackford, the SNP’s leader at Westminster, labelled the ruling a “democratic disgrace” and said the decision to exclude his party was to treat Scottish voters as “second-class citizens”.

Baroness Brinton for the Lib Dems called for televised leaders’ debates to be framed in “stronger legislation” and made clear her party would continue to fight for wider representation.

In an interview with The Herald, the PM was asked if he would ever engage the SNP leader in an election debate. He said: “Once Nicola Sturgeon takes leadership of her party in Parliament[ie Westminster] and is a serious contender to be Prime Minister of the UK that would be the appropriate moment.”

When it was suggested that meant he would never debate Ms Sturgeon, Mr Johnson replied: “The appropriate thing in this election is for me to contest the debates with whoever theoretically could be Prime Minister.”

Earlier this month at a rally in Glasgow, the FM asked why the PM and Mr Corbyn were “scared to debate me,” and issued a challenge, saying: “I’ll debate you anytime and anywhere and it will be for you to justify why Scotland can’t have a choice on our own future.”

Mr Johnson accepted the SNP leader could “very influential in our politics” but pointed out she had no seat in the Commons nor could she be PM.

“The candidate to be Prime Minister who Nicola Sturgeon would support is Jeremy Corbyn and that is why he is the appropriate person[to debate].”

Asked if he thought the FM was beneath him, Mr Johnson replied: “No, of course not. All I am saying is there is only one[other] person who can be Prime Minister and that is Jeremy Corbyn.”

Speaking from the Thatcher Boardroom in the Tories’ modern HQ in central London, a relaxed party leader seemed to relish the prospect of taking on his Labour foe, whom he once branded the “leader of a cabal of superannuated Marxists".

“I’m pumped up. I’m like a coiled spring,” he declared. Mr Johnson has apparently been practising hard for tonight’s clash; Michael Gove has been taking the part of the Labour leader in behind-closed doors run-throughs.

The PM also made clear he would continue to block Ms Sturgeon’s demand for a second referendum as a matter of principle.

“The people of Scotland were told emphatically in 2014 that this was a once-in-a-generation event, they would not be driven to the polls again and we should abide by that.”

Expressing his “absolute passion” for the Union, he said the economic arguments for Scotland remaining in it were overwhelming, noting how 60 per cent of Scottish trade was with the rest of the UK.

Asked if he was, therefore, making clear he would never agree to empower Holyrood to hold a second referendum, Mr Johnson said: “I’m ruling it out. It’s a bad idea.”

Asked if there were any circumstances in which he would change his mind, he replied: “No. People don’t think referendums are proving to be brilliantly healing as political devices in our country.”

READ MORE: Poll: Big majority of Brexiteers would accept Scottish independence as EU exit price

He argued the first step to healing the bitter divisions across the UK was to make people feel their democratic views were being honoured.

“So, when people voted to Remain in 2014 they should feel that democratic view is going to be honoured[for] as long as they were told[it was going to be]. And, similarly, people voted to leave the EU in 2016 and democracy should be observed. And that’s for me the most important thing. People on both sides of the argument do get that.

“We need our national debate to become less acrimonious…Feelings have been running high. The best way forward is to get Brexit done.”

Mr Johnson claimed a “fantastic opportunity” now lay before Britain.

“That’s why I am full of optimism about our Union and our prospects. Devolution has been a success, let’s be clear. It’s wonderful people should feel proud of Scotland and their Scottish identity; that’s a fantastic thing, a powerful thing, a good thing but I don’t want that to come at the expense of the UK, which is also a great thing. That’s where I am on this. There is a balance to be struck.”

Today in more electoral skirmishing, Labour claimed its analysis showed one in three UK billionaires, 48 out of 151, bankrolled the Tories as tax breaks for big corporations and super-rich nudged £100 billion. John McDonnell, the Shadow Chancellor, branded the connection "obscene".

But Simon Clarke, the Treasury Minister, stressed how the top one per cent of earners were paying a greater share of taxes under the Conservatives than at any time during the last Labour Government and that business tax receipts were at an all-time high, “meaning more money for public services”.

Meanwhile, Tory HQ launched its own attack on what it termed was “Corbyn’s tax raid on pensions”.

It claimed its analysis showed 10 million savers could lose an average of over £11,000 and be forced to delay retirement by almost three and a half years because of Labour’s plans for a Financial Transactions Tax and its desire to seize ten per cent of private firms.

“This is just one of the ways a Corbyn Government would hammer hardworking people on top of his plans to hike up taxes by £2,400 a year,” argued Therese Coffey, the Work and Pensions Secretary.

But Peter Dowd, the Shadow Chief Secretary to the Treasury, insisted it was no surprise big finance interests were “batting for the Tories in this election”.

He declared: “Boris Johnson’s Conservatives are backed by billionaires and bad bosses. The truth is that everyone will benefit from Labour’s plans to broaden ownership and make the UK a home for long-term, patient capital.”

Also today, the Green Party will announce 10 parliamentary Bills at its election manifesto, launch in London, to unleash a “green economic revolution” and secure a People’s Vote.

Jonathan Bartley, the party’s co-leader, said: “Today, we’re proud to put forward a manifesto which moves towards making our whole country carbon neutral by 2030, while delivering social justice across Britain.”

Yesterday at the annual CBI conference in London:

*Mr Johnson promised to cut employers' National Insurance and announced he was shelving a planned corporation tax cut from 19 per cent to 17 in a bid to divert £6 billion to the "priorities of the British people" like the NHS;

*Mr Corbyn pledged to create a climate apprenticeship programme which would train 80,000 people a year and raised the prospect of local authorities south of the border having the right to take bus services into public ownership;

*Jo Swinson insisted the Lib Dems were the "natural party of business" and remaining in the EU gave Britain the best chance of success and

*CBI chief Carolyn Fairburn warned that confidence in Britain was faltering amid "extreme ideology" on both sides of the political divide.