The above answers are not necessarily correct. What matters is who is the beneficial owner of the money in the account. If you & your father can prove it is your father's money, then this should be accepted.
However, it may be difficult to prove and you may well need help getting the DWP to accept the situation. See your local CAB, or other Welfare Benefits advice agency.
Incidentally, if the total savings are �12000 you might (even if you are unsuccessful in your appeal) still have an entitlement to Income Support, as the maximum allowable savings is �16000.