The Organisation for Economic Cooperation and Development said, on the other hand, Japan, the US and Russia continue to see improvement in their economic growth.
The latest readings are based on Composite Leading Indicators (CLIs) that provide early signs of turning points in economic activity of a country.
"The assessment for China and India has changed significantly since last month. For both countries, the CLIs point towards economic activity below long-term trend," OECD said.
CLI for India stood at 98 in April, lower than 98.2 recorded in March.
In April, China CLI slid to 99.1 from 99.4 seen in the previous month.
OECD's assessment comes at a time when concerns are rising that the Indian economy is losing momentum, especially after growth touched a nine-year low of 6.5 per cent in 2011-12.
Indian economy expanded 8.4 per cent for two consecutive years -- 2009-10 and 2010-11 -- even as many developed nations were ravaged by the 2008 financial meltdown during this period.
Of late, many global financial services majors, including Morgan Stanley, StanChart and Citi, have lowered their India's growth forecast. Their forecasts vary from 5.7 per cent to 6.4 per cent.
According to OECD, France and Italy are witnessing sluggish economic activities.
"The CLIs for Germany, Canada, the United Kingdom and the euro area as a whole continue to point towards economic activity slightly below long-term trend," it noted.
Further, the think tank said that in Brazil, the CLI continues to point towards a turning point with economic activity returning towards long-term trend but with a weaker intensity.