Robin Thicke has admitted that he didn't actually co-write his hit single Blurred Lines with Pharrell Williams.

The singer has testified as part of an ongoing legal case which claims the smash hit was lifted from Marvin Gaye's 1977 song Got To Give It Up.

According to a copy of the deposition obtained by The Hollywood Reporter, Robin admitted the recording session for the song was all a bit of a blur.

Robin testified: "I was high on vicodin and alcohol when I showed up at the studio... I wanted some credit for this big hit. But the reality is, is that Pharrell had the beat and he wrote almost every single part of the song."

Pharrell said in his deposition he was "in the driver's seat" for the song, but explained that sharing credit is the norm for the music industry. "You know, people are made to look like they have much more authorship in the situation than they actually do. So that's where the embellishment comes in."

When asked whose words were used in the lyrics, Pharrell answered: "Mine."

Pharrell also said it is "Robin Thicke's voice" that made the song a hit: "Because it's the white man singing soulfully and we, unfortunately, in this country don't get enough - we don't get to hear that as often, so we get excited by it when the mainstream gives that a shot."

Robin also admitted he had previously lied in an interview about how Marvin Gaye had inspired him.

He had said in an interview with GQ magazine: "Pharrell and I were in the studio and I told him that one of my favourite songs of all time was Marvin Gaye's Got To Give It Up. I was like, 'Damn, we should make something like that, something with that groove.' Then he started playing a little something and we literally wrote the song in about a half hour and recorded it."

Asked why he lied, Robin stated that he "had a drug and alcohol problem for the year" and "didn't do a sober interview".