Growth in six core infrastructure industries dropped to 4.3 per cent in July 2008-09 from 7.2 per cent a year ago, which economists feared could stunt the expansion of an already slowing economy.

Crude oil was the worst performer in the grouping with a negative growth of three per cent in July 2008 against a positive trend in the comparable month of last fiscal.

Finished steel was the other poor performer, logging a growth of 1.9 per cent against 10.8 per cent.

However, petroleum refinery products stood out in the pack, expanding by 11.8 per cent for the month under review in 2008-09, against 4.7 per cent in July last year. For the April-July period this year, the growth declined to 3.7 per cent from 6.6 per cent a year ago.

"It is a poor performance...it will become a constraint on the overall economic growth. Infrastructure has to be supportive," D K Joshi, Principal Economist, CRISIL said, adding that poor performance of the power sector remained a grave concern.

Amidst year-on-year drop in the infrastructure growth, the pace of expansion in these industries that have 26.68 per cent weightage in the overall Index for Industrial Production was the highest in July compared with the last three months of this fiscal. The growth number for June was 3.4 per cent.

"The growth rate of five sectors other than the refinery products should be raised much higher, if these are not to emerge as critical constraints on the Indian economic growth," ICRIER Director Rajive Kumar said.

Poor performance of infrastructure industries could have a bearing on overall industrial production and in turn on economic growth, which the PM' EAC feels would slow down to 7.7 per cent this fiscal. GDP growth in 2007-08 was 9 per cent.