BORIS Johnson has ruled out debating Nicola Sturgeon ahead of the December 12 General Election.

The Prime Minister said he would not debate the SNP leader as she is not "a serious contender to be prime minister of the UK".

Speaking at Tory HQ in London, Johnson also ruled out granting a Section 30 order to allow a second Scottish independence referendum while he is in Downing Street.

When asked if he would debate Sturgeon, Johnson replied: “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.”

The former London mayor was then asked if that meant he would not debate her at all. He replied: “The appropriate thing in this election is for me to contest the debates with whoever theoretically could be prime minister.”

Johnson denied he thought Sturgeon is beneath him, adding: "All I am saying is there is only one[other] person who can be prime minister and that is Jeremy Corbyn.”

Tonight Johnson will debate Corbyn head-to-head in an ITV debate after legal challenges from the SNP and LibDems to include them fell through.

SNP Westminster leader Ian Blackford said the decision was discrimination against Scottish voters, treating them as “second-class citizens”.

READ MORE: SNP and LibDems slam decision as they lose ITV debate fight

Later, the Tory leader insisted he would not grant the powers for a Scottish independence referendum to take place while he is PM. 

He said: “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.”

Johnson, who has taken on the title of Minister for the Union, added: “I’m ruling it out. It’s a bad idea.”

He was asked if there was a scenario in which he would change his view. “No. People don’t think referendums are proving to be brilliantly healing as political devices in our country.”

The PM added he is optimistic about getting Brexit done. He said: “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.”