Q: Do husband need permission to take second wife?‏

A: If they had an agreement at the time of the marriage (nikah) that permission would need to be sort by the husband, then in such an instance he would have to ask for her permission.

If they did not have such an agreement, he can attain another wife without her permission.

Allah Certainly Knows Best.

p.s. This above applies to those countries that allow for a second wife situation.