Appears to be that the government will pay tenant deposits of up to £1,500 or £2,000 in London more or less directly to landlords, without asking the landlord for the money back; if they can't get the money back from the tenant, the government will just write it off.
So presumably those landlords who currently would have demanded a smaller deposit will promptly bump it up to £1,500.
See how many other holes you can spot in Clegg's logic.