Pauley Perrette is best known as the 'goth chick' on the smash CBS drama NCIS.

But the actress is also becoming one of the most visible straight allies in the fight for LGBT equality.

Perrette, who plays quirky forensics expert Abby Sciuto on NCIS, said this week that she and fiancee Thomas Arklie, a former Marine, will not get married until California's Proposition 8 is struck down and same-sex couples are also allowed to wed.

She wrote to her more than 200,000 Twitter followers this week: 'Me & #MyMarine are totally engaged now but will NOT GET MARRIED UNTIL #Prop8 is OVER.'

She later added: 'We're Not getting married because Prop 8 is unjust. But having blast being engaged. He re-asks me everyday & I say Yes.'

Perrette describes herself as a 'civil rights activist' on her Twitter page. She is a frequent presence at LGBT benefits and rallies and is a big supporter of the NOH8 silent protest photo campaign which celebrates its third anniversary Tuesday night with a party in West Hollywood.

The 42-year-old actress was the single individual fund raiser, among 30,000 participants, at last fall's 27th annual AIDS Walk Los Angeles event.