Professor Rob Adams, a world-renowned urban designer, has told a government panel charged with overseeing the new building rules for CBD designs that, while it was not too late to preserve the quality of Melbourne, change could not be left any longer.

"If we fail to [put in appropriate controls] the quality of the whole city will incrementally decline and we will have squandered the value and amenity that has been built up over the last 180 years," he said.

"Changing the controls now … is exactly the right time to time to do it. Leave it any longer would possibly open up the city to going beyond the point of reasonable repair."

His warning echoes that of RMIT planning academic Michael Buxton, who said Melbourne's high-rise CBD construction boom will continue unabated despite the Andrews government's attempt to rein in its worst excesses.

The state government, he said, had become heavily dependent on the construction boom continuing, with property tax revenue accounting for four times that of gambling taxes.

Professor Adams, who has overseen a number of city-shaping projects at the Melbourne City Council, said he was concerned about the cumulative effect of skyscrapers that failed to respect the "fine grain" quality of Melbourne's streets.

He said the vast tower walls that faced onto streets were unpleasant for pedestrians, exacerbated wind problems and cut off access to sunlight.

"You can either have a situation where every development that goes into Melbourne makes it better or you can go the other way and say every development that goes into Melbourne makes it slightly worse and then the outcome is going to be a city that is not as good as the one we have today," he said.

Minimum tower setbacks are part of the Andrews government's proposed central city controls, while the reforms could also go some way to address another issue raised by Professor Adams – very tall towers on relatively small sites.

More than 60 per cent pf planning permits granted in the Hoddle Grid and Southbank between July 2010 and October 2015 were on blocks less than 1500 square metres and 31 per cent were less than 800 square metres.

"So we have increasingly high developments and smaller and smaller blocks," Professor Adams said.

He questioned if it was appropriate to build towers on any block, however small, in Melbourne - a trend that was resulting in the loss of smaller buildings such as old hotels.

Under the proposed rules, to be finalised in September, developers who do not provide public benefit will need larger blocks to get approval to build taller towers.