The City of Stonnington is flush with nightclubs, shops and socialites. What it doesn't have a lot of, is parks. And so it has set out to acquire some.

Council has launched a $200,000 feasibility study and is test drilling this week to explore turning Cato Street car park in Prahran into a park.

But parking officers shouldn't weep just yet or greenies rejoice - the council plans to move the car park under the park, which could increase the number of parking spaces from the current 400.

Mayor Adrian Stubbs said the car park may have to be at least two levels deep to make it viable.

The cost would be ''millions'' but council will wait until the feasibility study's report comes out in May. Council could finance it or seek private, federal, or, in an election year, state government funding.

Cr Stubbs would like an underground car park to offer shoppers the first two hours free, and sees the park as a village square, flanked by cafes and shops as well as the current supermarkets.

He said it would be a boon to locals. ''It gives residents a place to congregate, socialise. You'd see mums walking with their prams, it's a place to engage in sporting activity, it's a place just to sit and think. Would you rather have asphalt, or trees and grass? I'd rather have trees and grass.''

The move came from concerns that of Stonnington's 26 square kilometres of land, only 6.7 per cent is public open space. It is the second-lowest ratio after Glen Eira at 4.5 per cent, and compares to an average 17.9 per cent in metropolitan Melbourne.

Cr Stubbs said because it was so ''mammothly behind'' the council ''needs to be creative'' to increase the percentage. It has identified 450 sites for investigation, including taking a 100-space car park in Edsall Street, Malvern, underground, if Cato Street proved successful.

Cato Street and Edsall Street car parks are both council-owned.

Stonnington also has a $28.1 million reserve fund for 2013-2014 alone for the purchase of open space, raised from developers who subdivide property having to contribute to council 5 per cent of the land's unimproved capital value towards open space, if they don't contribute actual open space. Since 2007 the fund has purchased six properties, many adjoining parks, five of them worth more than $1 million, says Cr Stubbs.

Council has also applied for an acquisition overlay for vacant privately owned land in Carters Street, Toorak, and for vacant factories between Bangs Street and Clifton Street, Prahran, to signal council's desire to purchase when it is sold in future. Other options being considered include buying railway land or building decking over it, creating ''pocket parks'' in dead-end streets and creating roof gardens.

Oskar Cebergs, spokesman for the Chapel Street Precinct Association, said the 6.7 per cent open space figure was ''pretty frightening''. The association was ''fully supportive'' of the open space strategy, including the greening of Cato Street car park. But building the car park shouldn't be a priority over the council's revitalisation of Chapel Street, including new footpaths, lighting, town squares, furniture and greening.