He was questioned by police at Teddington station over allegations of rape and sexual assault dating back to 1995.
The unnamed woman claims he forced himself on her during a party held at his home in Sheen, west London.
The former host of ITV's This Morning was acquitted in 2003 of 2 counts of indecent assault on a 23-year-old actress in May 1997.
A Metropolitan Police spokesman said of the current allegations: 'Officers are investigating an allegation of rape and indecent assault on a woman dating from November 1995.
'At approximately 7pm this evening a man aged in his 40s attended a London police station by appointment and was arrested in connection with the inquiry.
'He was interviewed and bailed pending further inquiries to a date in late August.'
John, 43, denied the new allegations, the Sun newspaper said.
It reported the accuser was in her early 20s when she claims she was attacked.
Where to next?
- Information on post traumatic stress disorder