As it is not considered as a gift deed, the declaration letter signed by you spouse would be enough.
PS: guys please do not confuse PoF obtained through a gift deed and PoF under the name of spouse.
Exactly! Think about this --- if a husband has to move to court to use funds in her wife's name, it essentially means breakdown of marriage which in principle invalidates the joint application.
Thus, in a joint application, husband and wife need not get things done legally between themselves. A simple declaration should be good.