Sir Paul said his drug intake was "never excessive"

"I didn't realise I'd taken it - I was just handed something and smoked it," he told Uncut magazine, adding: "It didn't do anything for me."

The musician said he also took cocaine "for about a year" but was "never completely crazy" about the drug.

In an interview published in this month's Uncut, Sir Paul admitted drugs "informed" much of the Beatles' music.

He said the song Got To Get You Into My Life was "about pot - although everyone missed it at the time", and Day Tripper was "about acid".

I was never crazy with cocaine, especially when you start getting those terrible come-downs

Sir Paul McCartney

But the singer said it was "easy to overestimate" the influence of drugs on the Beatles' material.

"Just about everyone was doing them in one form or another. We were no different," he said.

"But the writing was too important for us to mess it up by getting off our heads all the time."

'Pills'

Sir Paul said he felt "lucky" he had not taken to heroin as he "wouldn't have fancied heading down that road".

He added the "terrible come-downs" had eventually persuaded him to stop using cocaine.

According to the singer, The Beatles started experimenting early in their career - "right back to the Hamburg days when there were all these pills going around".

Sir Paul said drugs like pot and LSD "informed" the Beatles' music

Sir Paul also revealed that he and fellow Beatle John Lennon had dabbled with another addictive substance during their schooldays - tea.

"We'd stuff some Twining Tea in a pipe, smoke that and write songs."

McCartney's drug use made headlines in January 1980 when he arrived at Tokyo's Narita Airport for an eleven-date tour with his band Wings.

Deported

The singer was arrested after customs officials discovered half a pound (225g) of marijuana in his luggage.

He spent 10 nights in a Japanese prison before being released and deported.

Sir Paul now admits "it was the daftest thing I've done in my entire life".

McCartney (right) was arrested in 1980 while touring with Wings

"This stuff was too good to flush down the toilet, so I thought I'd take it with me."

He said it was "not too wonderful" being held in a Japanese jail, but he kept his spirits up by organising "sing-songs" with his fellow prisoners.

"I don't actually smoke the stuff these days," he told Uncut. "It's something I've kind of grown out of."

But he said he was flattered when he was recently invited by a group of Los Angeles teenagers to share their marijuana.

"To me, it's a huge compliment that a bunch of kids think I might be up to smoke a bit of dope with them."