Litigation funder IMF Bentham plans to back a class action against the Australian Defence Force over the Williamtown contamination scandal.

A firefighting chemical used by the Williamtown RAAF base, 30km north of Newcastle, five years ago has been found to have polluted groundwater and soil at the base and in the surrounding residential area.

Now Williamtown residents want to sue the Defence Department.

A statement from IMF Bentham on Tuesday says it plans to fund the class action that will be conducted by Gadens Lawyers.

“IMF’s funding of the class action is conditional on sufficient claimants with valid claims signing funding agreements with IMF,” the statement said.

In February, a parliamentary inquiry has recommended the Turnbull government compensate commercial fishermen affected by the contamination.