The Government has failed to gain enough support for its "fix-it" bill for police use of hidden cameras and has watered down its retrospective nature to win the votes of Labour and Act.
The concession means that evidence gathered by hidden cameras in 47 pending trials - involving 229 suspects - will remain illegally obtained.
Such evidence can still be admitted under the Evidence Act, which enables a judge to allow improperly obtained evidence after weighing up factors such as the seriousness of the charge and the intrusiveness of the cameras.
The amended Video Camera Surveillance (Temporary Measures) Bill, which was reported back from the justice select committee last night, now has the numbers to pass under urgency on Thursday with the support of Labour, Act and United Future.
The bill will make covert video surveillance by state agencies legal, subject to the Bill of Rights Act protection against unreasonable search and seizure.
Once it is passed, police will apply for new search warrants and switch on hidden cameras in 13 operations that have been idle for over a month.
They were turned off after a Supreme Court decision on September 2 that ruled that all covert video surveillance on private property was illegal.
The National Party majority on the committee wanted the bill to be fully retrospective, but that would have struggled to win the majority support of Parliament.
"The rest of the committee was not on board with that, and it's important that legislation is enduring, even though it's a short time-frame," said committee chairman and National MP Chester Borrows.
He believed the safeguards in the Evidence Act were enough to ensure serious criminals would not go free.
A spokesman for Attorney-General Chris Finlayson said the priority was to properly empower the police before the house rose on Thursday.
The bill will also ensure that previous convictions cannot be challenged on the basis of the Supreme Court ruling, closing the door on a potential slew of appeals.
It will be in effect for only six months, rather than the proposed 12 months, sending a clear message to the next Parliament that it must make the Search and Surveillance Bill a priority.
The bill has been tweaked to explicitly state that all video surveillance - including "over the fence" surveillance - is subject to the Bill of Rights Act protections.
The Government has accepted the recommendations.
Under the bill, state agencies will be able to use hidden cameras on private property under a Summary Proceedings Act search warrant, which is granted in the District Court to investigate crimes that carry a potential jail term.
Mr Borrows said the bill reinforced current practice: police are expectedto state their intentions to use video surveillance in applying for awarrant, which is approved by aDistrict Court judge for investigating serious crimes.
* State agencies, including police, can legally use hidden cameras on private property under a warrant - a practice the Supreme Court said was illegal.
* Old convictions cannot be appealed against on the basis of the Supreme Court ruling.
* Evidence gathered for pending trials will have been obtained illegally, but is admissible at the court's discretion.
* Applies for only six months so the next Parliament can pass the Search and Surveillance Bill, which has stronger protections.