Amar Jeet Kaur, CPI leader and National Secretary of All India Trade Union Congress (AITUC), condemned the remarks and urged the apex court to "urgently correct the verdict".
"A Delhi court verdict that pre-marital sex is immoral and against the tenets of every religion holding that every act of sexual intercourse between two adults on the promise of marriage does not become rape is shocking...," she said in a statement issued to the media.
Additional Sessions judge Virender Bhat passed judgement while acquitting a man, 29, in a rape case in which the woman had alleged that the man, whom she had met through a chat website in July 2006, used to have physical relations with her on several occasions by promising to marry her.
The woman, doing a secretarial and administrative job at a private company here, had lodged a complaint of rape against him in May 2011 after the man refused to marry her.