The Police Association, the Maori Party, Labour and NZ First leader Winston Peters have also questioned the 1994 conviction.
Pora was convicted of Ms Burdett's rape and murder in 1994 and was again found guilty at a retrial in 2000. This was ordered after the semen in Burdett's body was found to belong to Malcolm Rewa, the country's second-most prolific rapist and someone who otherwise always attacked alone. Rewa was eventually convicted of Burdett's rape, but two juries couldn't decide about murder.
Both Prime Minister John Key and Ms Collins have said the Government would stay out of the way until the appeal process was exhausted.
Ms Collins told RadioLive a ministerial inquiry was not possible as Pora's lawyer, Jonathan Krebs, was seeking an acquittal or pardon.
"That can't be done by any ministerial inquiry. It has to be done through either a pardon [which is] what he's already started to apply for or through the Privy Council which he's also said he's applied for,'' she said.
High profile lawyer Peter Williams QC yesterday said Pora could be released immediately if a resolution was passed by Cabinet pardoning the conviction.
"That was the procedure that was used in Arthur Allan Thomas' case,'' he told RadioLive.