Metallica's James Hetfield has taken aim at bandmate Kirk Hammett for his work on 'Hardwired... to Self-Destruct'.

James Hetfield

James Hetfield

The heavy metal band's frontman has hinted he has some doubts over the lead guitarist's "claims" that he lost 250 riffs he'd written for the group's 10th studio album when he mislaid his iPhone in 2015.

Speaking on the Meltdown podcast, he said: "That's what he claims. I'm sure he did [lose the phone], but it doesn't make sense that he wouldn't have [the music] on his computer, either.

"But, whatever ... Yeah, Kirk had some riffs that he ... I guess submitted -- it's not a very nice word to be used if you're in a band.

"But you know, we all submit our tapes, and we sit there and we listen to them and we pick the best stuff. There was not much stuff from Kirk. Whether his phone was lost, or whatever ..."

This comes after the 53-year-old singer previously admitted Kirk wasn't involved in the writing process for the record, and that his riffs "weren't there".

Last year, he said: "Kirk was not part of the writing. Kirk obviously came in and did the solos. Lars and I always have done this, but with contributions from other people on their riffs and things.

"Kirk's riffs weren't there."

Kirk, 54, previously admitted he was devastated after losing his phone and didn't have the device backed up.

He said: "I was crushed. It didn't get backed up. When it happened, I was bummed out for about two or three days."

Metallica are also made up of drummer Lars Ulrich and bassist Robert Trujillo.