A man and a woman who picked up two young women from the streets of Hamilton, gave them cannabis and alcohol and raped them, have had years added to their jail time by the Court of Appeal.

Jason Lloyd Jones was convicted of raping two women in the space of six weeks in 2009 and 2010, and sentenced to nine years and six months jail.

Maureen Samantha Iti was convicted of being a party to the second rape, after she held the victim down so Jones could rape her, and sentenced to four years and eight months jail.

The Crown appealed both sentences saying their were "manifestly inadequate" and that Jones should have been given minimum period of imprisonment.

The appeal court agreed, in a judgment released on Friday, and increased Jones's sentence to 13 years.

Jones had earlier convictions for assault and sexual intercourse with a girl aged 12 to 16 years, though he had not seriously offended for about 20 years.

It had not been appropriate for the judge to reduce his sentence for "previous good conduct", the court said.

Jones also said the rapes were consensual sex, so the judge should not have given him credit for remorse.

The court also added a minimum no parole period of six years to Jones's sentence, because the Judge's assessment that he was "most unlikely to offend again", seemed to fly in the face of trial evidence and ignored that Jones was a serial offender, who had not accepted he had done anything wrong.

The court increased Iti's sentenced by one year, to five years and eight months jail, because her participation in the crime was "very serious".