Published: 1:49 PM July 26, 2019 Updated: 6:06 PM September 17, 2020

Amid warnings that he may be the 'last prime minister of the United Kingdom', Boris Johnson has invented a new ministerial role and promptly given it to himself.

Johnson had previously claimed in the Scottish Mail on Sunday before his arrival at Number 10 that he wanted the role of prime minister to also ensure the United Kingdom stays together.

He wrote for the newspaper: "I believe the occupant of No. 10 should be not just prime minister and first lord of the treasury and minister for the civil service," he wrote during his leadership campaign. "He or she should be minister for the union as well."

Now, as Scotland's first minister Nicola Sturgeon and her Welsh counterpart Mark Drakeford issued warnings about the union's future, a spokesperson for Number 10 has confirmed that Johnson has created the role and appointed himself.

A spokesperson for No. 10 said: "The PM has set out that he is going be the leader for the whole of the United Kingdom and he wants to unite the country and unleash the productive power of every corner of England, Wales, Scotland and Northern Ireland."

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The spokesman added that Johnson had first told cabinet about the appointment on Thursday.

"It is a statement of his commitment to the strengthening of the union and the value he places upon it," the spokesman added.

In calls with Nicola Sturgeon and Mark Drakeford, Johnson was warned he would face stiff resistance if he sought to leave the EU without an agreement with Brussels.

Drakeford made it "emphatically clear" that a no-deal Brexit would be "catastrophic" and cause "profound damage" while Sturgeon reiterated the Scottish government's "strong opposition" to a no-deal Brexit and urged the prime minister to change course.

They both penned a letter to shortly after his appointment to say it would be "unconscionable" to have a no-deal Brexit.

On Johnson's new job title, SNP MSP Tom Arthur said: "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."