A campaign demanding the resignation of United States (US) labour secretary Alexander Acosta was gaining traction Thursday, days after a newspaper investigation revealed he secretly approved a reduced sentence for billionaire sex offender Jeffrey Epstein.

Business tycoon Esptein, 65, was convicted a decade ago of abusing dozens of young girls in Palm Beach, Florida but avoided life behind bars to serve just 13 months in a county jail.

Last week, a Miami Herald investigation reported then-federal prosecutor Acosta approved a secret deal in 2008 for the short sentence.

The so-called “federal non-prosecution” agreement saw Epstein plead guilty to two prostitution charges.

According to a lawsuit against him, he had recruited poor teenagers to carry out “massages” which led to abuse, paying them $200 to $300.

The Herald demanded in an editorial on Thursday that Acosta step down — branding him “ethically compromised.”

“We are recommending that Acosta resign his current position for allowing a rich, powerful, politically connected man to avoid justice and get off easy,” the editorial argued.

In the wake of the Herald’s investigation, released last week, an online petition demanding Acosta’s resignation has amassed 70 000 signatures.

Meanwhile, the newspaper reported over two dozen lawmakers are demanding Acosta be investigated for misconduct.