BORIS Johnson has said he will take the title of minister of the Union if he becomes prime minister.

But his commitment to what he called the most “successful political and economic Union in history” was undermined by his refusal to commit to the Barnett Formula.

Over the weekend, his rival Jeremy Hunt said was “essential” to maintain the mechanism used to decide the size of Scotland’s block grant.

His spokesperson said: “The Barnett Formula is essential to protect Scotland’s public services. That’s why a government run by Jeremy would maintain it, to help ensure Scotland’s schools and hospitals get the funding they need.”

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Johnson, former mayor of London, has long attacked the money coming to Scotland from the Treasury.

In 2006 he claimed it produced “deeply inequitable outcomes”.

Three years later, he described it as a “system of amazing political antiquity by which the English taxpayer sends about £20 billion every year to Scotland as a kind of present”.

In 2012, he called for money heading to Scotland to come to London: “If London isn’t moving, the UK is nowhere. A pound spent in Croydon or Tottenham, the areas hit by the riots last year, will generate far more for the rest of the economy than a pound spent in Strathclyde.”

A spokesman for the Scottish Tories said: “The Barnett Formula works for Scotland and works for the UK. Any candidate must either commit to it, or set out a very detailed plan for an upgrade.”

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Writing in the Mail on Sunday, Johnson, who remains by quite some considerable distance the most likely candidate to replace Theresa May, said the “cost-free but symbolically important” title of minister of the Union would “underscore the importance” of the UK.

Meanwhile, Hunt has said he too would take the UK out of the EU with no deal at the end of October.

On BBC One’s The Andrew Marr Show, Hunt admitted the decision would not be popular in Scotland, but he insisted he was still the best man to strengthen the UK.

“At the beginning of October, if there is no prospect of a deal that can get through parliament, then I will leave at the end of October because that is our democratic promise to the British people,” Hunt told BBC One’s The Andrew Marr Show.

“There are risks,” the Foreign Secretary conceded. “You think about what someone like Nicola Sturgeon would do politically if we had a no-deal situation and we would have to get through that, and that is why a no-deal Brexit is not my first choice.”

The National:

Last week, Hunt, during a visit to Peterhead, was asked if Brexit or protecting the Union was his priority. He replied: “The Union every time.”

Yesterday, however, he said it was not a question of a prime minister choosing between Brexit or the Union.

“If you send to Brussels someone who can negotiate a deal that can get through parliament, then you won’t have a no-deal situation, and then you reduce those risks,” he added.

“But I’m also very clear that we are going to leave the European Union come what may and I will deliver that. If that happens, I will do it in a way that protects the Union because it’s absolutely vital that we do.”

The SNP MSP Tom Arthur said it was outrageous that the Tories were “now plotting to use Brexit as an opportunity to railroad systematic cuts to Scotland’s budget – offering a grim insight into what Scotland can expect from the next Tory prime minister.”

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He added: “The Tories have longed for the opportunity to hammer Scotland’s budget for years – but the people of Scotland won’t stand by while Westminster politicians plot to cut money from our vital public services to fund their disastrous no-deal Brexit.

“Yet again the mask has slipped and fatally undermined the Tories’ attempts to portray themselves as working in Scotland’s best interests.

Boris Johnson’s latest scheme to appoint the next Tory leader as minister of the Union is simply laughable – voters will see this meaningless gimmick for what it is.

“With the hard right-wing of the Tory Party threatening to axe the Barnett Formula and slaughter Scotland’s public services it’s time to take our future into our own hands.”