Gordon Matheson said the cuts to benefits, from housing to disability allowances, were not reform but a cruel attack.
Mr Matheson made his remarks when he addressed a conference on welfare reform in Glasgow, which was attended by Work And Pensions Secretary Iain Duncan Smith, the main driving force behind the planned changes.
The Glasgow leader said governments had to help get people into work and help create the jobs for them to go to.
However, he said that forcing people who are unable to work off benefits and into the employment market when jobs are scarce was a "folly" and urged the Government to alter its course.
He said: "I used to think the word 'reform' had a kind of warm feel to it. I used to think it meant tackling entrenched privilege and ending ancient abuses.
"I didn't think it could be a cover for the pauperisation of our most vulnerable. But I'm afraid that is exactly what it has come to mean."
Mr Duncan Smith said there was more to do and warned of further reform to tax and benefits to end the perception that it was not worthwhile leaving benefits for a low-paid job.
But Mr Matheson said reform had to improve people's lives, not make them pay in the pursuit of a political agenda.
He said: "I accept the need to streamline the welfare system, which had become cluttered.
"What I cannot accept is the unrelenting pace of the reforms.
"Cutting benefits and forcing people on to the market can only possibly succeed when there is work to go to. Ploughing on regardless is cruel folly.
Reform is about tackling disadvantage and unfairness, not treating society's most vulnerable with punitive and cruel attacks."