www.bbc.com/…
see also: British local and municipal elections are upcoming on the 2nd of may
British ex-health undersecretary defects from Tories to Labour
Mr Yousaf has been struggling to secure support to lead a minority government.
He is due to face two confidence votes this week - one in him personally, the other in his government.
The first minister's decision last week to end the SNP's deal with the Greens followed a backlash over the SNP's decision to scrap 2030 climate targets.