Mr Yousaf, the Scottish Health Secretary, is one of three candidates in the running to take over from Nicola Sturgeon as SNP leader, alongside Finance Secretary Kate Forbes and former community safety minister Ash Regan.

"In this election, it has to be Humza," Mr Blackford said.

The Ross, Skye and Lochaber MP said Mr Yousaf was the person to bring the party together amid divisions over matters such as gender recognition reforms and the strategy for independence.

Mr Blackford, who stepped down as SNP Westminster leader in December, said: "We need a figure who will unite both the SNP and the Yes movement.

"As a nation, we require a first minister who will ensure that we deliver in government and lead us forward to guarantee Scotland's voice is heard in an independence referendum.

"Humza is that leader."

He added: "He has demonstrated his ability to lead in political office across a host of roles within the Scottish government.

"Importantly for me, we need to get our economy moving in the face of this Tory cost of living crisis and create the sustainability, economic growth and better-paid jobs that will help Scotland thrive.

"I'm looking forward to working with Humza to make sure that we deliver for Scotland and send a message that this is a country where people want to do business."

Read more:
Humza Yousaf says absence from gay marriage vote 'dragged up' for political reasons
Kate Forbes 'burdened' by hurt caused by religious views

Several leading SNP figures have already backed Mr Yousaf, including Scottish Social Justice Secretary Shona Robison, Education Secretary Shirley-Anne Somerville and SNP Westminster deputy leader Mhairi Black.

However, a Panelbase poll for The Sunday Times put Ms Forbes in the lead, with 23% of those questioned saying they wanted her to take the top job ahead of 15% for Mr Yousaf and 7% for Ms Regan.