The family of Auckland woman Folole Muliaga plan to sue both Mercury Energy and Middlemore Hospital over the mother of four's tragic death.

Legal papers are to be filed at the Auckland High Court seeking financial redress from Mercury and the hospital regarding Mrs Muliaga's death, which followed power being cut to her Mangere home in 2007, Fairfax media reported.

Mrs Muliaga, 45, a morbidly obese woman, was using a mains-powered oxygen machine and died three hours after a contractor to Mercury Energy disconnected her power over an unpaid bill of $168.40.

In findings released in 2008 following an inquest, Coroner Gordon Matenga found that the action of cutting Mrs Muliaga's power on May 29 2007 was a factor in her death.

Mercury later presented the Muliaga family with $10,000, but now lawyer Olinda Woodroffe is reported to be seeking more.

Mrs Muliaga's widower Lopaavea Muliaga said he wanted closure for himself and his children.