If I am forced to have sex with a female other than my wife due to blackmail, what should be my plan of action according to Islamic laws? If I do not comply with the woman's demand she will destroy my family life.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

What we understand from the question is that you are asking what you should do if a woman asks you to commit adultery or fornication with her and threatens you if you refuse to do so. The answer is that it is not permissible for you to accept her demand or respond to her threat, and it is forbidden for you to commit adultery or fornication with her. The fact that she is threatening you is not considered as being absolutely forced to do so.

Ibn Al-'Arabi said: “If a man is forced to commit adultery or fornication or be imprisoned, it is not permissible for him according to the consensus of the scholars to do so, but if he is forced by being beaten, then the scholars differed in opinion on this.”

Some scholars said even if he is threatened to commit adultery or fornication or be killed, he is still not allowed to commit this sin. Also As-Sarakhsi [from the Hanafi School of jurisprudence] said: “If he is threatened to be killed or to commit adultery or fornication, it is still not permissible for him to do so.”

So, even if a person is threatened to be killed, he is still not allowed to commit adultery or fornication, then how could he respond to a threat which is far less than being killed.

To conclude, you are not allowed to respond to the threat of this woman and it is forbidden for you to do so. Allaah Says (what means): {And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.}[Quran 17:32]

So you should fear Allaah and be patient, and if you fear to be killed or the like, then you can inform the authorities so that they would protect you. This is the correct and appropriate behaviour and procedure.

Allaah Knows best.