A 30-year-old woman recently alleged that the former minister and his son Adarsh repeatedly sexually exploited her last year and the visuals of the alleged acts were telecast by TV channels here.
Thettayil's wife Daisy held a brief press conference and said that her husband was innocent.
"We will approach the speaker and governor with a complaint and also approach the police to prove that he and our son was being politically targeted," said Daisy, as she broke down.
To repeated questions on her husband's whereabouts, she said she did not know anything.
The complainant said Thettayil promised her that he would get his son married to her, but did not keep his word.
"He should resign as legislator and face the case," said the woman in an interview to a TV channel telecast ahead of Daisy's news conference.
Thettayil, who represents the Angamaly constituency in Ernakulam district, has stayed away from public glare since June 23 after the visuals of the alleged sexual exploitation were telecast on TV.
Soon after the filing of the complaint by the woman, Thettayil, a Janata Dal-Secular legislator, denied the allegation and accused her of morphing his picture along with her.
While Thettayil's party is backing him, leaders of the Left Democratic Front, to which Thettayil belongs, seem divided over the issue.
Communist Party India-Marxist state secretary Pinarayi Vijayan said there had been similar allegations against other legislators in the past and none had resigned, so Thettayil's resignation was ruled out.
Vijayan's party colleague and Leader of Opposition V.S. Achuthanandan and the Communist Party of India have asked the former minister to quit.