Hanover Finance is arguing two trustee firms should shoulder part of the damages being sought by the capital markets watchdog.
Former Hanover boss Mark Hotchin and other directors and promoters are being sued for $35 million by the Financial Markets Authority.
The lawsuit involves prospectuses issued between 2007 and July 2008 that the regulator claims were misleading.
Mr Hotchin said Guardian Trust and Perpetual failed in their duty of properly monitoring Hanover and should have put it into receivership earlier.
Both trustees want the action thrown out before the authority's case goes to trial.
The lawyer for Guardian Trust, Ralph Simpson, said the trustee's role was not to vet prospectus statements but to ensure the company did not breach its trust deed.