Sir Elton John has branded Michael Jackson 'mentally ill' and 'disturbing to be around' in his new memoir, Me.

Elton John developed a friendly relationship with Michael early on in his career, but has now admitted that over the years, he became concerned about the way in which he started to 'sequester himself away from the world'.

He wrote: 'I’d known Michael since he was 13 or 14... He was just the most adorable kid you could imagine.

'But at some point in the intervening years, he started sequestering himself away from the world, and away from reality the way Elvis Presley did.'

Elton continued: 'God knows what was going on in his head, and God knows what prescription drugs he was being pumped full of, but every time I saw him in his later years I came away thinking the poor guy had totally lost his marbles.'

He added: 'I don’t mean that in the light-hearted way. He was genuinely mentally ill, a disturbing person to be around.'

Recalling a time he invited Michael to one of his parties, Elton claims the star wandered off and was found playing with his housekeeper's son, prompting Elton to surmise: 'For whatever reason, he couldn’t seem to cope with adult company at all.'

Michael suddenly of an overdose of sedatives administered by his personal physician, Conard Murray, in 2009.This year, the star was posthumously accused of child sexual abuse by two men who were friends with him as youngsters in the documentary Finding Neverland.