AMAZON FOUNDER JEFF Bezos drew criticism yesterday when he thanked Amazon workers after his brief trip to the edge of space yesterday.

“I want to thank every Amazon employee, and every Amazon customer because you guys paid for all this,” the 57-year-old said during a news conference after becoming the second billionaire in just over a week to ride in his own spacecraft.

Bezos built Amazon into a shopping and entertainment behemoth but has faced increasing activism within his own workforce and rising pressure from critics to improve working conditions.

Labour groups and Amazon workers have claimed the company does not offer its hourly employees enough break times, puts too much reliance on rigid productivity metrics, and has unsafe working conditions.

An effort to unionise workers at an Amazon warehouse in Alabama failed earlier this year.

Robert Reich, former secretary of labour under President Bill Clinton and a professor of public policy at University of California, Berkeley, wrote on Twitter that Bezos had crushed unionising attempts for decades.

“Amazon workers don’t need Bezos to thank them. They need him to stop union busting — and pay them what they deserve,” Reich wrote.

Bezos stepped down as Amazon CEO in July, allowing him more time for side projects including his space exploration company Blue Origin. He has said he has financed the rocket company by selling one billion dollars (€851 million) in Amazon stock each year.

After the spaceflight, Bezos awarded 100 million-dollar (€85 million) donations through a new philanthropic initiative to both Washington DC chef Jose Andres and CNN contributor Van Jones to put towards any charity or non-profit organisation of their choice.

Jones has founded a number of non-profit organisations and Mr Andres’s non-profit group World Central Kitchen provides meals to people after natural disasters.

Nevertheless, House Representative Earl Blumenauer, who is on the tax-writing Ways and Means Committee, proposed on Tuesday legislation that would tax space travel for non-scientific research purposes.

“Space exploration isn’t a tax-free holiday for the wealthy,” said Blumenauer, an Oregon Democrat. “Just as normal Americans pay taxes when they buy airline tickets, billionaires who fly into space to produce nothing of scientific value should do the same, and then some.”

Others tied his spaceflight to reports Bezos has not paid his fair share of taxes. According to the non-profit investigative journalism organisation ProPublica, Bezos paid no income tax in 2007 and 2011.

“Jeff Bezos forgot to thank all the hardworking Americans who actually paid taxes to keep this country running while he and Amazon paid nothing,” Democratic Senator Elizabeth Warren tweeted.