A target of 7000 new homes in Wellington over five years is almost impossible to meet, the city council's own buildings portfolio leader says.

Mayor Celia Wade-Brown and Housing Minister Nick Smith signed the Wellington Housing Accord on Tuesday.

The accord gives Wellington City Council the power to create special housing areas where consents are fast-tracked and building can take place with little public consultation.

The aim is to increase housing supply to keep up with demand and provide more affordable homes.

But councillor Iona Pannett, the buildings portfolio leader, has come out against the accord as it stands.

Pannett said the target of 7000 new homes over five years - double the current rate of building - was almost impossible to reach and the council was setting itself up to fail.

She is likely to propose three amendments to the accord at today's extraordinary council meeting, where it is due to be ratified.

These would renegotiate the target and ensure new building would be accompanied by adequate infrastructure and would not substantially alter existing neighbourhoods.

"It makes us look like monkeys," she said. "This is an agreement where we are going to fail."

But Wade-Brown said the accord was one of a number of tools the council could use to ensure housing affordability.

Advice to the council calls the target "ambitious" and says new areas for development may have to be found to meet it.

"Regardless of the council's best efforts, the targets may not be met," it said.

The special housing areas may need to be set up away from areas targeted for development such as Johnsonville and Kilbirnie.

"New areas may also need to be identified and consulted on in order to achieve the target."

Pannett said the accord did not give sufficient weight to infrastructure - a concern raised by Johnsonville Community Association vice-president Graeme Sawyer and property expert Olly Newland.

She supported intensification but said it had to be done carefully. "We don't want the slums of tomorrow being created. People are suspicious about our ability to deliver quality building . . . we need to be able to show faster consenting does not mean poor quality."

Council advice noted the lack of opportunity for public submissions or Environment Court appeals on proposed developments within special housing areas.

"Some negative public reaction is anticipated from people who will no longer be able to submit in opposition to a development," it said.

Council spokesman Richard MacLean said areas within five minutes' walk of Johnsonville and Kilbirnie shopping centres and Adelaide Rd from the Basin Reserve to Riddiford St were candidates.

Developers would find specific sites within those areas and then seek the council's agreement to create a special housing area.

Over the next few months developers would be asked about other possible sites and what plans they had. "There are no definite lines on maps yet."