The Labour Party says the Government could have saved taxpayers a great deal of money for the Rena disaster clean-up if it had passed laws making shipping companies liable.
The container ship ran aground on Astrolabe Reef off the coast of Tauranga on 5 October last year, spilling oil and debris into the sea and polluting beaches in the area.
Maritime New Zealand documents released to Labour under the Official Information Act show the estimated cost of the clean-up has escalated to $50 million.
Environment spokesperson Grant Robertson says the Government was advised by a select committee in 2008 to incorporate two international conventions on damage liability into New Zealand law.
But he says it failed do so and, as things stand, the country could be up for another $50 million tomorrow if another ship grounded off the coast.
Mr Robertson saysfellow Labour MP Phil Goff has a private member's bill in the ballot that would make ship owners more liable for damages and the Government is welcome to pick it up.