Latest estimates put total insured losses from the Gulf of Mexico oil spill disaster between $US4-6 billion ($4.4-$6.6 billion), a fraction of the estimated $US35 billion ($38.3 billion) in total economic losses.

Global consultancy Towers Watson says the insured losses pale in comparison with other large disasters and will not be enough to constitute a “watershed event” for property and casualty insurers.

With litigation from the disaster likely to take decades to resolve, Towers Watson predicts the companies directly involved in the spill will, at the very least, draw upon the full value of their policies.

Rig owner Transocean has $US945 million ($1.03 billion) of insurance coverage on the rig, as well as liability cover of $US950 million ($10.4 billion). Joint venture well operators Anadarko Petroleum and Mitsui have $US163 million ($178 million) and $US45 million ($49 million) in cover respectively.

As has been widely reported, BP has no commercial liability insurance for the event, instead relying on its captive insurer.

Other parties that may be judged liable include Cameron International, the manufacturer of the well’s blowout preventer, which has liability cover of $US500 million ($546 million), and Haliburton, which was responsible for cementing the well and had $US600 million ($656 million) of liability cover.

The combined total of the coverage limits above is $US3.3 billion ($3.6 billion), but Towers Watson expects directors’ and officers’ liability and workers’ compensation losses will further increase costs, as will the involvement of other companies drawn into litigation.