The Centre for Social Justice (CSJ), which faced an angry backlash over its pension proposal, has received up to £150,000 from tycoon Sir Brian Souter's personal charity, it is understood.
Founded as an independent think tank in 2004, the CSJ was set up by former Tory leader Iain Duncan Smith after he visited Easterhouse in Glasgow.
The organisation, which has strong links to the Conservatives, aims to put social justice "at the heart of British politics" and makes policy recommendations.
The CSJ, which does not publish details of all the donations it receives, has financial ties to Souter, according to The Herald on Sunday.
The businessman, who founded the Stagecoach bus empire, is a high-profile Scottish Nationalist who has donated over £2 million to the SNP.
He and his wife Betty also set up a charity, the Souter Charitable Trust, which focuses on projects that promote spiritual welfare and poverty reduction.
According to the SCT's latest accounts, the Souter charity gave a £50,000 grant to the CSJ in 2018 and pledged another £100,000.
Strongly associated with the welfare reform agenda pursued when Iain Duncan Smith was the Secretary of State for Work and Pensions, the CSJ describes itself as the "architects" of the universal credit policy.
The CSJ's latest proposal was to suggest a rise in the state pension age to 70 by 2028, before another increase to 75.
It argued: "Working longer has the potential to improve health and wellbeing, increase retirement savings and ensure the full functioning of public services for all."
It was that noted the average life expectancy for men in Glasgow is around 73, raising the prospect of some dying before they access their state pension.
In a motion at Holyrood, SNP MSP Sandra White said the plan would have a "disproportionate" impact on poorer people in Scotland and claimed it was a "further attack" on the elderly.
Asked what the SCT funding was for, a spokesman for the CSJ said: "This funding helps support the CSJ which does research into the prevention and alleviation of poverty as per the charity's and our own objectives."
The SCT has been contacted for comment.