The MSP has faced a barrage of criticism after it was revealed that Glasgow-based United Wholesale (Scotland), which was built from scratch by his father, did not pay the real living wage to all staff.
Nicola Sturgeon made reference to the row at First Minister’s Questions on Thursday, with the SNP leader claiming there was “a massive gulf - a gulf as wide as the Clyde - between what Labour says and what Labour does”.
With several trade unions confirming this week their support for Richard Leonard, the left-winger and rival candidate for the party leadership, Mr Sarwar was under pressure from his backers to regain momentum as the contest heats up.
He has voluntarily waived his right to any dividend and will now be unable to access the assets or take any remuneration for his lifetime.
Although senior politicians have previously placed shares in a blind trust that can be accessed at a later point, Mr Sarwar will go even further and has signed a discretionary trust deed that means he can never access the assets.
The beneficiaries of the trust will be Mr Sarwar’s three young children, who will not access the assets until they are adults.
In a statement, he said: “I will never apologise for being my father’s son. I am incredibly proud of his achievements, building a company that now employs around 250 workers – many in Nicola Sturgeon’s own constituency.
“Scotland has cradled my family, nurtured it and gave it opportunity and success.
“And it’s the Labour Party that allowed them to share that success to help others. I’m in the Labour Party because of those values and because I know our party remains the single best vehicle for change in this country.
“That’s why I have dedicated my life to fighting for the values I believe in.
“In this contest, it’s only right that Labour members can hear my plans to rescue our NHS, invest in education, reverse Tory benefit cuts, tackle gender inequality, strengthen Scotland’s place in the UK, and lift tens of thousands of children out of poverty.
“I am ready to go toe-to-toe with Nicola Sturgeon, because our country needs a First Minister who will deliver equality, opportunity and fairness for all.”