The final bill is expected to be about £30m
The Maritime and Coastguard Agency's costs come on top of almost £17million spent so far recovering the 17,000-tonne Transocean Winner.
The final bill is expected to be about £30m.
The massive rig grounded on Lewis during a storm on August 8 and remained there for two weeks before it was refloated and taken to Turkey for scrap.
A spokeswoman for the MCA said that its costs for responding to the incident "are in the region of £400,000".
The MCA said its bill covered such costs as the use of helicopters, planes, salvage advice and staff.
It does not include the services of the police and other public services involved in responding to the grounding.
The operation to recover the rig has already cost Transocean $21m, according to its latest financial statement.
It is likely the bill will soar because the rig only arrived in Turkey on November 1 – more than a month after the end of the third quarter reporting period by Transocean.
The massive rig grounded on Lewis during a storm on August 8 and remained there for two weeks
Transocean has already paid compensation to local fishermen affected by the incident and donated £120,000 to the community.
A Transocean spokesman said the firm was splitting the cash in two ways – £60,000 is earmarked to help the Dalmore and Carloway community where the rig grounded.
The rig was being towed from Norway to Malta when it broke free from the tugboat Alp Forward and crashed into the shore at Dalmore Bay, near Carloway.
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Two of its four fuel tanks ruptured in the collision and spilled about 53,000 litres of diesel into the sea.
Most of the pollution is believed to have dispersed harmlessly but the damage suffered by the rig when it grounded meant it was too hazardous to attempt a second tow.