Use of Security Deposit to Pay Rent Arrears

Tenancy Deposits

After the tenant vacated the property, my Agent used the Security Deposit to pay the rent arrears without consulting me, this is despite the fact that I pay rent indemnity insurance to a subsidiary of their company. In addition, the Landlord's Security Deposit Consent form was sent to me a few days after they used the deposit. Now I am a few hundred pounds out of pocket for what the Checkout Inventory, prepared by them, classed as unreasonable wear & tear because there is not enough money left to cover the damages.

Should the agent reassess the situation or are they correct in what they have done, if they are incorrect what should my next step be?

I have contacted them by phone and email but they remain oblivious to my situation.