The State Government's controversial stop and search legislation is effectively dead after the Nationals announced they will not be supporting it.

The government needed the support of three of the five Nationals MPs in the Upper House for the bill to pass, but today all five announced they will be voting against it.

Nationals MP Colin Halt says the Police Minister Rob Johnson offered to make more amendments to the bill to win their support.

However he says the Nationals believe the laws are not necessary.

"It's not needed," Mr Halt said.

"They've got existing legislation. We don't need additional powers to achieve the same result."

The laws would have given police the power to search anyone in a declared area without consent or reasonable suspicion.

The Police Minister Rob Johnson offered further compromises on the bill in a last-ditch attempt to win the Nationals' support.

He says he will put the Bill on hold until 2013 but insists that the legislation is not dead.

"I'm very disappointed because I believe this legislation is brought in to save lives," Mr Johnson said.

The WA Police Commissioner Karl O'Callaghan says he's also disappointed the legislation will not be passed.

"I think we've missed some opportunities," he said.

"My understanding according to what the Police Minister is saying is that it may go ahead at some future time, but we won't have it for the summer now I wouldn't imagine, so we'll just work on the legislation we've got."