Czech drug-smuggler Karel Sroubek will stay behind bars after being denied parole.

The Parole Board, in a just released decision, said assessment by Serco of Sroubek possessing a "low risk of reoffending" had underestimated the risk.

Factors the board deemed highly relevant to the risk he posed include: that his offending involving an attempted sophisticated importation of drugs into New Zealand from the Czech Republic, his association with criminals in the Czech Republic and his association with the Hells Angels in New Zealand.

Sroubek first came to New Zealand in 2003 on a false passport in the name of Jan Antolik.

He was found guilty in a 2011 jury trial of using a false passport and lying to immigration officials, but was discharged without conviction by the trial judge, who believed his evidence.

The representative kickboxer claimed he had to flee his home in the Czech Republic in fear of corrupt police officers and a criminal after witnessing a murder.

Four years later he was jailed for five years and nine months for bringing a drug used to make Ecstasy into the country hidden among legitimate goods. He is due to finish his sentence in early 2022.

"We acknowledge, as far as Mr Antolik is concerned, that overall he has behaved well within prison," Parole Board chairman Sir Ron Young said in the decision.

"We also acknowledge that it is hardly his fault or responsibility that he has not had any rehabilitation programmes because Serco have assessed him at low risk of reoffending."

But it was not a view shared by the Parole Board.

"We do not think it is low at all. Given the matters we have identified above, we think it is significantly higher than low.

"We think there is evidence to support the fact that Mr Antolik [Sroubek] has a significant history of illegal activity in both the Czech Republic and New Zealand and spread over many years."

While the Parole Board considered not all of the offending was illustrated by formal convictions, some of it was violent and dishonest.

"Given that intensive past history we think he remains an undue risk.

"We do not consider any of the proposed special conditions significantly affect that risk.

"Parole is therefore declined."

The Parole Board has invited Serco to re-assess Sroubek's risk before his next appearance in January.