Douglas Ross has insisted it is healthy for politicians to have "robust" debates after being questioned about his frustrations with Boris Johnson.

The Scottish Conservative leader said voters don't expect their politicians to be clones who agree on everything, adding: "I know that's quite alien to members of the SNP."

He said he would challenge the Prime Minister – and be challenged by him – if he doesn't think he has taken the right approach for Scotland. 

It comes after Mr Johnson reportedly said Scottish devolution has been a "disaster north of the border" in a conference call with northern Tory MPs, and called it "Tony Blair's biggest mistake".

Mr Ross said the Prime Minister has made clear he believes in devolution, but he has "frustrations" with how Scotland is being run under the SNP.

Speaking during a Q&A at the Scottish Tories' virtual conference, he said: "I don't think it's the worst thing in the world for people to see and understand that you can be in the same party but you can look at things in different ways. 

"And actually we can work together where it's in the best interests of Scotland, and we can challenge each other. 

"He'll challenge me and I'll challenge him if we don't think we've taken the right approach for Scotland. 

"I think it's healthy that we can have that debate, we can articulate that debate, and can come to a conclusion that yes, we both ultimately and positively believe in devolution, but there are aspects of that that haven't delivered for Scotland over the last 13 and a half years of the SNP being in power.

"And I say that about having this debate, and robust debate, because I think it's natural. 

"People don't expect their politicians to be clones and all agree the exact same thing at the exact same point. 

"Now I know that's quite alien to members of the SNP because they're not allowed, due to their constitution, to take a different approach from the Scottish leadership. 

"I think it's healthy to challenge leadership sometimes, because ultimately that gets the best decisions and the best results for people in Scotland."

He added: "I think you need that robust debate. We'll never progress anywhere if we all just agree with each other, and that's the nature of politics."

Mr Ross insisted the Prime Minister listens and takes on board comments. 

He said: "Every time I sit down with the Prime Minister, whether it's physically or virtually, when we speak on the phone - yeah, he does listen, he takes it on board, and we move on and progress from there."