Ahead of a visit to one of the online retail giant’s distribution centers in Alabama on Friday by Senator Bernie Sanders, Clark took a jab at the Vermont senator, who has lobbied hard for a rise in the federal minimum wage to $15 an hour.

But Clark defended his company’s working conditions, tweeting: “I often say we are the Bernie Sanders of employers, but that’s not quite right because we actually deliver a progressive workplace.”

Pocan shared the tweet and referred to previous claims made about the company’s practices which include tough production quotas, long workdays and not enough breaks.

“Paying workers $15/hr doesn’t make you a ‘progressive workplace’ when you union-bust & make workers urinate in water bottles,” Pocan wrote.

“The truth is that we have over a million incredible employees around the world who are proud of what they do, and have great wages and health care from day one,” it added.

In a follow-up tweet, it said: “We hope you can enact policies that get other employers to offer what we already do.”

When contacted for comment, Pocan’s office referred Newsweek to follow-up tweets the congressman had posted. In one, he wrote, “but you do union-bust?” and in another, he wrote: “and yes, I do believe your workers. You don’t?”

This story has been updated to include a response to Newsweek from Rep. Pocan’s office.