But Nash then sought assurances from police about their behaviour, and said today that police had not divulged any information to Immigration NZ about the address of Sroubek's estranged wife.
Immigration NZ confirmed that they already knew where she was and police did not provide the information.
"Further, I was advised the address where she lives is not a police safe house, but that police have contacted her several times to verify what assistance she needs or what complaints she wishes to make," Nash said.
"The story being put about by Mark Mitchell is not correct."
But during Question Time today and speaking on behalf of the Prime Minister, Deputy Prime Minister Winston Peters said that police had offered protection to her on three occasions - but she had declined.
He said the National Party was chiefly responsible for compromising her safety by referencing her in 23 oral questions and 56 public statements.
"In short, you've got someone who - for political purposes, venal political purposes at that - is being used as a trump by Opposition members. If protection and secrecy and privacy are called to this issue, then the National Party has been a major offender."
Following Question Time, Mitchell told the Herald that Peters and Nash were wrong.
"There was definitely a police protection plan put in place for her. We organised that through Minister Stuart Nash. She had gone to a house where she thought she would be safe, and that was part of the plan."
He said regardless of whether Immigration NZ already knew her address, it was wrong to show up unannounced.
"This is not a woman under investigation from Immigration. She's a Kiwi. Why are they turning up on her doorstep in a house that is part of a police plan?
"If that is their standard practice, then it seriously needs to be reviewed because all it can be seen as is bullying from the state."
Mitchell said her fears were based on Sroubek's criminal history and gang associations. He has also alleged in the House that Sroubek has made threatening phone calls to her.
He rejected Peters' claim that the National Party had increased those fears.
"The Opposition has a job to do, and if people come to them for help, we will do that.
"The reason the information has come out is because the Deputy PM stood up in the House and tried to attack her character, and called her a National Party informant. That's why she asked us to speak up for her."
Police said it would not comment on individual cases.