Misuse Of Power Of Attorney

My father had inherited huge debts as excise duty payable. I had handed over a power of attorney in his name for a self-earned property for the purpose of selling the property and settling the debt. (There is no evidence on record stating that the property had been given for this purpose). However, my father using the power of attorney gave away the property to my mother as a settlement deed. I became aware of this about 3 years ago but I did not take any action for this. Is this transfer valid? Will I still be able to get this registration canceled.