Labour MP Kelvin Davis says he is being denied access to the watchdog for New Zealand's prisons and is alleging political interference from Corrections Minister Judith Collins.
Collins, however, says she had absolutely no say in the Corrections Department's decision not to grant Davis a meeting with the prison inspectorate.
Davis sought a meeting last month, saying that he wanted to better understand the role that prison inspectors played.
After several delays he was told on Monday that no meeting would take place, he said.
A letter to Davis from Corrections' chief executive of corporate services said: "I appreciate your interest in the role and the function of the Department's Inspectorate team.
"However, I do not support this meeting with a member of the Department's Inspectorate team."
He was instead provided with some fact-sheets about the inspectorate's work, which is to check whether inmates are being treated fairly and humanely, and hearing prisoners' complaints.
The Corrections Department stood by its decision today, saying that it was made in the interests of political neutrality.
"Corrections staff are bound by the State Services Code of Conduct which includes expectations around political neutrality of public servants," a spokeswoman said.
"This is why it was not considered appropriate for this meeting to take place."
If the Labour MP had any specific concerns he could direct them to the Corrections Department, the spokeswoman said.
Davis said he suspected interference by Collins, though he had no evidence for this.
"She's worried I'm going to find out more about what's going wrong within Corrections and she wants to avoid political embarrassment."
A spokeswoman for Collins said the allegation was "completely false" and that the decision was made by Corrections alone.
"The Minister's Office had absolutely no involvement in the consideration of the request of the response," she said.
Last year, Davis embarrassed Corrections when he revealed in Parliament that organised violence was taking place within Mt Eden Correctional Facility, including alleged "dropping" of newly incarcerated inmates from balconies within the prison.
The practice of dropping was never proven, but the confirmation of "fight clubs" within the jail eventually led to private prison operator Serco losing its management contract and to the demotion of former Corrections Minister Sam Lotu-Iiga.