Disgraced former politician Phillip Field has failed to overturn his conviction on fraud charges or have his six-year jail sentence reduced.

Field was jailed in October last year after being convicted by a jury in the High Court in Auckland of 11 charges of bribery and corruption as a Member of Parliament and 15 charges of perverting the course of justice.

He was charged after then prime minister Helen Clark ordered an inquiry into allegations Field had traded immigration favours for tiling, painting or plastering work on his properties in New Zealand and Samoa by Thai nationals.

The Court of Appeal released its decision today and said Justice Rodney Hansen had correctly interpreted the law, directed the jury and allowed evidence.

It also found the convictions were right and the sentence should be upheld.

The perversion of justice charges were very serious, the finding said.

"Mr Field had been manipulative and adaptive and not only lied himself, but procured others to lie as well and create false documents in an endeavour to head off the consequences of his wrongdoing. Had he succeeded, serious criminal offending would likely have gone undetected.

"The High Court judge was therefore correct to reflect those concerns in the sentence imposed on Mr Field.

Field remains in prison.