Chinese companies have an incentive to avoid taxes or boost export rebates by misreporting sales and profits.

NPR: China's Struggle To Measure Economy Clouds Outlook

They fear that China, through an undervalued currency, trade barriers and state subsidies to its exporters - in the form of cheap land, cheap loans, export rebates and other help - is hollowing out US industry and jobs.

BBC: China accuses the US of Olympic hypocrisy

Mr Thornton added that "there is plenty of anecdotal evidence to suggest that exporters are faking orders and 'round-tripping' in order to gain government export tax rebates".

BBC: China's March trade deficit may signal key import shift

"Chinese exporters may have over-reported their value to get export credit rebates because the figures in Hong Kong to and from China do not add up, " Mr Lun claimed.

BBC: China's March trade deficit may signal key import shift

"Chinese exporters may have over reported their value to get export credit rebates because the figures in Hong Kong to and from China do not add up, " he said.

NPR: China's March Imports Rise In Sign Of Recovery