China could overtake the United States to become the world's largest economy as early as 2020, a top business consultancy said on Thursday, underlining the "seismic change" in global economic power.

PriceWaterhouseCoopers (PWC) also said in its report that by 2030 the top 10 world economies could be China, followed by the United States, India, Japan, Brazil, Russia, Germany, Mexico, France and Britain.

The current 10 largest economies, according to 2008 data from the International Monetary Fund, are the United States, Japan, China, Germany, France, Britain, Italy, Russia, Spain and Brazil.

The report also pointed to an increasing share of global GDP taken up by China and India, compared to the United States and the European Union.

The proportion in 2010 will be 20 per cent for the US, 21 per cent for the EU, 13 per cent for China and five per cent for India, PWC said.

But by 2030 that will have changed to 16 per cent for the US, 15 per cent for the EU, 19 per cent for China and nine per cent for India, it added.