Pop star Justin Bieber has opened up about his “heavy drug use” online.

In a lengthy Instagram post, Bieber described remorse about his much-chronicled troubles and brushes with the law.

“I was 18 with no skills in the real world,” he wrote, “with millions of dollars and access to whatever I wanted.”

“By 20 I made every bad decision you could have thought of.”

He went on to describe a period of “doing pretty heavy drugs”, in which he “abused all of [his] relationships”.

Bieber has repeatedly shown contrition for his youthful behaviour in recent years, which included multiple arrests, fights with press photographers and footage of racist jokes.

The most notorious incident was his 2013 visit to the Anne Frank Museum in Amsterdam, where he wrote in the guestbook that he hoped Frank “would have been a Belieber” – one of the singer’s devoted young female fans.

In a long interview with Vogue this February, Bieber called his younger self “arrogant and cocky”, as well as “lonely”.

He has not released a new album since 2015, citing his wish to take a “hiatus” from music. During his spell away from the limelight, he married model Hailey Baldwin, daughter of actor Stephen .

Earlier this year, at the Coachella festival in California, Bieber confirmed that he is working towards an eventual fifth album, which as yet has no release date.