The organisation’s monthly billings index, created by surveying the AIAs member practices, reported its first positive results for four months in August with a score of 51.4.

A score of 50 points or more indicates month-on-month growth.

But the latest results for September have shown a sharp fall in demand for design services and consequent billings with a score of 46.9.

"It appears that the positive conditions seen last month were more of an aberration,"said AIA chief economist Kermit Baker.

"The economy is weak enough at present that design activity is bouncing around more than usual; one strong month can be followed by a weak one. The economy needs to be stronger to generate sustained growth in design activity."

The project inquiries index also fell sharply from 56.9 to 54.3, although growth remains positive.