Anas Sarwar has branded Boris Johnson “a disaster” and said the Prime Minister is the “biggest threat to the United Kingdom”.

The Scottish Labour leader said the reason Johnson is unlikely to come on the Holyrood campaign trail is that he is liability for Conservatives in Scotland.

Sarwar said he fully expects UK leader Keir Starmer to return to Scotland before the May 6 election while Scottish Tory leader Douglas Ross said on Monday he did not expect the Prime Minister to come to Scotland to campaign for his party.

Previously the Prime Minister said ““wild horses” could not keep him away from the Scottish campaign but the Tories are now using covid travel restrictions, which will be lifted on Monday, as an excuse.

Sarwar said: “I can understand why Boris Johnson doesn’t want to visit – Boris Johnson is a disaster, devolution is not a disaster.

“Boris Johnson is the biggest threat to the United Kingdom, Boris Johnson has delivered us Brexit and things are so bad that even Ruth Davidson has walked away.”

Sarwar said: “Keir Starmer has been up in the campaign, I think you can see who’s an asset and who’s not.”

When pushed on whether Starmer would return to Scotland, he said: “We’ll see – my intention is that I believe he is going to come back up.”

Sarwar, who made a speech to the online annual Scottish Trade Unions Congress on Tuesday, said he wanted to focus on a “positive campaign”.

He vowed to will “work with anyone” to set up a minimum income standard in Scotland after unveiled his party’s social security proposals ahead of the Holyrood elections.

Labour’s plans include the doubling of the Scottish Child Payment to £20 per week, but also assessing a minimum income threshold below which Scots would not be allowed to fall beneath.

A spokesman for the Scottish Tories said: “While we stand up to the SNP and fight their reckless referendum plans, the Labour party would rather cosy up to them.

“Anas Sarwar and Keir Starmer are too weak and cannot be trusted over Scotland’s place in the United Kingdom.”