Police are reviewing an investigation into the death a young Christchurch mum for the second time after doubts were raised over her partner's version of how she died.

Libby Francis McKay, 27, died in hospital on June 14, 2013, from severe injuries that her partner Michael Brown said occurred when she fell from his Toyota Hilux ute while he was driving on Christchurch's Halswell Junction Rd.

Brown helped police with their investigation and told them he did not push her from the ute.

He later moved to Australia and refused to return to New Zealand to give evidence at her coronial inquest.

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Coroner David Crerar concluded that McKay died from "high energy impact injuries to head and brain with pneumonia complicating coma".

He found that with the evidence available, including the interpretation of forensic pathologist Dr Martin Sage, her injuries were consistent with having exited the ute and hit the road.

However, the coroner said there "outstanding questions" that could have been answered by Brown "if he attended a further inquest hearing".

Last month, Chief Coroner Judge Deborah Marshall announced she would review the coronial file relating to McKay's death.

McKay's mother, Pauline Webby, told TVNZ's Sunday programme that she commissioned an independent report into the crash after doubts over how her daughter died.

Webby said Australian-based company Accident Analysis reconstructed the crash and conducted tests which cast doubt of Brown's story.

Independent crash investigator Tim Stevenson told Sunday that if McKay had fallen from a moving vehicle he would have expected to see extreme abrasions to her head, knees, elbows and shoulders.

Webby called for the investigation into McKay's death to be reopened, while Judge Marshall asked to see the Australian report.

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Today, Nelson MP Nick Smith released correspondence with Mike Bush, Commissioner of Police, which showed that police are looking to review their investigation.

Police have also requested a copy of the Accident Analysis report commissioned by Webby so they can "review the investigation in its entirety to determine the appropriate next court of action which will include making contact with the family of Ms McKay in person to discuss their expectations".

The matter has been "referred with urgency" to Canterbury District Commander Superintendent John Price who has assigned oversight of the investigation to Canterbury District Manager Criminal Investigations, Detective Inspector Corrie Parnell.

"Our intent is to ensure this investigation is informed by all available information which will encompass considering the relevancy of any fresh evidence and pursuing all positive lines of inquiry," Bush told Smith.

A 2016 police review of the case found no evidence to suggest anything suspicious was behind McKay's death.

Today, Smith welcomed the response, saying police and the coroner need to reopen the inquiry after the family's expert analysis found Brown's explanation "untenable".

"This expert report needs to be reviewed and witnesses re-interviewed to establish what caused the tragic death of this 27-year-old woman and to ensure justice is done," Smith said.

"Police are not infallible and need to be prepared to have another look at difficult cases when fresh evidence comes to light.

"There are too many inconsistencies in this case for this tragedy to be left unquestioned. I will be continuing to support the family in their endeavour to get answers and justice for Libby McKay."