Two Mongrel Mob members who gave key evidence against gang members say their safety is at risk in prison and their sentences should be shortened.

Saul Waihape and Vincent Monika were inside the gang's Wairoa headquarters when a rival faction from the gang raided with firearms in August 2010.

Waihape and Monika both fired shots.

The pair were key Crown witnesses against the six members of the rival faction.

Without their co-operation the charges against the six would not have been brought.

Last year, Waihape was sentenced in the High Court to four years jail and Monika was sentenced to five years and three months.

They appealed their sentences last week, arguing they should have been entitled to a reduction of 45 per cent to their sentences for their co-operation, not just the 30 per cent they were given.

Waihape's lawyer, Nigel Hewat, said: "It was probably the first time in Mongrel Mob history that a member has broken their code of silence and testified against fellow Mob members." This had put their personal safety in danger.

Both were at risk in prison from fellow inmates and this had made their sentences more onerous, Mr Hewat said.

The Court of Appeal found the sentences were adequate given the men's significant previous convictions had not been treated as an aggravating factor and dismissed the appeal.

The convictions of the other six gang members were overturned in the Court of Appeal last week.

A retrial has since been ordered.

- © Fairfax NZ News