Twenty people were arrested in the UK in an operation by the National Crime Squad, Scotland Yard and West Midlands Police.

Officers believe money was paid into banks in the Midlands from across the UK and was then sent electronically to Hong Kong and other overseas destinations.

More than 200 officers were involved in the UK end of the operation - code-named Diorite - and targeted addresses in north and west London, Walsall and Coventry.

We believe that large sums of cash, in some cases tens of thousands of pounds, were paid into banks here and then transferred to Hong Kong Detective Chief Inspector Paul Owen

They seized up to �150,000 in cash, along with documents and computer equipment.

Police in Hong Kong made seven raids and an address in America was also being searched.

Detective Chief Inspector Paul Owen, from the Telford branch of the National Crime Squad, said: "We believe that large sums of cash, in some cases tens of thousands of pounds, were paid into banks here and then transferred to Hong Kong.

"It is still too early to give exact figures about the total sum of money involved, but our investigations would suggest that in excess of �10m was processed."