Justin Bieber has admitted to feeling “like a fraud” in a candid social media post that has sparked fresh concern among fans over his wellbeing.

The 31-year-old singer shared his thoughts in an Instagram post on Thursday, March 13 after months of speculation about his physical and mental state - and the status of his marriage - revealing struggles with imposter syndrome.

He said: “People told me my whole life, ‘Wow, Justin, you deserve that’. And I personally have always felt unworthy, like I was a fraud, like when people told me I deserve something.

“It made me feel sneaky, like, damn, if they only knew my thoughts. How judgmental I am, how selfish I really am... they wouldn’t be saying this.

“I say all this to say, if you feel sneaky, welcome to the club. I definitely feel unequipped and unqualified most days.”

Bieber first found fame aged 15 after being discovered on YouTube and signing to his friend and mentor Usher’s record label.

His debut single “Baby” was released in 2010, catapulting him to international stardom.

Since then, he has become one of the world’s best-selling music artists, with an estimated 150 million records sold globally.

Speculation over his health has intensified in recent months following appearances where he looked unkempt, prompting his representative to deny claims he was using hard drugs.

Despite the speculation, Bieber and his wife, Hailey Bieber, 28, who share a seven-month-old son, Jack Blues, have continued to present a united front.

The couple has been seen together in public and on social media, including a post on March 1, celebrating Justin’s 31st birthday.

However, concerns were reignited days later when the singer shared images of himself smoking from what appeared to be a bong.

The photos, posted to Instagram, showed him sitting on an e-bike with Cypress Hill’s “Hits from the Bong” playing in the background.

Last month, Justin’s representative addressed concerns over his appearance, saying in a statement: “The recurring narrative that Justin is using hard drugs is absolutely not true.”

The representative insisted the musician was “in one of the best places in his life," focusing on parenting and making new music.