Lord Mayor Lisa Scaffidi has accused the City of Subiaco of scaremongering over the newly adopted City of Perth bill, and insists new ratepayers will be better off financially under her council.

Key points: City of Perth will expand its boundaries on July 1

City of Perth will expand its boundaries on July 1 Lord Mayor says new residents will pay lower rates

Lord Mayor says new residents will pay lower rates Dismisses concerns neighbouring Subiaco will be $4m worse off

Dismisses concerns neighbouring Subiaco will be $4m worse off WALGA says staff need clarity on job futures

The Government's contentious City of Perth bill passed State Parliament late yesterday, meaning the capital city's boundaries would expand on July 1.

The bill passed the Legislative Council more than a year after the Government was forced to abandon its wider metropolitan municipality reform when ratepayers in East Fremantle, Kwinana and South Perth voted against proposed amalgamations.

City of Perth has welcomed the legislation which sees it take in land occupied by the University of Western Australia, Kings Park, the QEII Medical Centre.

"This is going to enable and empower us ... to do strong economic promotion, nationally and internationally, with work in developing medical research opportunities and encouraging international students to choose Perth," Mrs Scaffidi said.

The city also gained residential areas home to about 3,000 people who were previously in the City of Subiaco.

"They will be better off financially with the City of Perth.

"They will probably have less rates to pay, they'll have a very professional service even though I say so myself, and we will be ensuring they will be feel very welcomed very quickly."

The Subiaco council said yesterday it would be about $4 million per year worse off and under significant financial strain.

Mrs Scaffidi said she did not accept that argument.

"The City of Subiaco are saying that they are going to be financially impacted, I can't accept that because they are losing 3,000 residents, there might be more per household, but it should not financially cripple Subiaco," she said.

"We've been reviewing their financial situation and I think that really its been a lot of scaremongering on their part."

Unanswered questions remain, WALGA says

Mrs Scaffidi said critics of Perth expansion needed to grasp the positive impacts of the changes.

"I think people need to be brutally honest and accept that these kinds of changes are for the greater good, this is about efficiency and innovation," she said.

WA Local Government Association (WALGA) president Lynne Craigie said there were several impacts from the legislation that had not been considered by the Government.

"How will this affect the staff of both councils? How it affects the communities?" she said.

"Things like staff redundancies ... obviously there is going to be oversupply in one and not enough in the other, does that mean that staff will transfer over?

"That sort of stuff that hasn't been outlined clearly."

Ms Craigie believed there should have been a committee already set up to deal with those issues.

"My concern for both councils is that I don't know that the State Government has thought through an implementation plan, the costing of and how these things will come about," she said.

"I am hopeful that we will hear from the Planning Minister in the next few days as to how this will be implemented."

Local Government Minister Tony Simpson dismissed Ms Craigie's concerns.

"If WALGA had been following the debate in Parliament and were familiar with the Local Government Act, they would be aware of the transitional provisions and protections for employees," he said in a statement.

"I understand that the CEOs of the City of Perth and City of Subiaco have had preliminary discussions.

"I am confident they will work together to ensure a smooth transition for both staff and residents in Subiaco."