Prince Charles has again weighed in on the subject of British cities by blaming “sick building syndrome” and poor urban planning for social and health problems.

He said that health difficulties including obesity, allergies and asthma could be linked to the “cavalier attitude” shown by planners and the building industry.

He told delegates at a conference on the environment in London:

“We are beginning to see that when we build badly, it doesn’t only affect the health of the natural environment, it affects our own health as well.”

He added: “We are slowly discovering that if we plan our towns and cities with the car at the centre of the design process, instead of putting the pedestrian at the centre and thereby creating attractive and well-organised human-scale neighbourhoods, it is likely to have an adverse effect on, for instance, obesity, heart disease, asthma and respiratory diseases.”

He said that neighbourhoods with a strong “public realm”, such as town squares, and a mix of shops and recreational areas seemed to have much higher levels of what sociologists call “social capital”.

The prince’s intervention follows a conference on this kind of “new urbanism” at his Prince’s Foundation in November, when he denounced town planners of the 1960s for “watered-down Le Corbusier”. It also follows deputy prime minister John Prescott’s apparent endorsement of new urbanism at the urban summit this month.

RIBA president George Ferguson said he broadly agreed with the prince but rejected his specific criticisms about the “cavalier attitude” of planners.

He said: “I agree with his statement but, if anything, he’s generalising too much. The architectural profession cares a lot about these issues and he must make allowance for the good things that have happened as well as the bad.”