Several City law firms were thrown into chaos following the revelation last week that police are investigating six of them for links with organised crime.
The National Criminal Intelligence Service (NCIS) is refusing to identify the firms involved, which has created a climate of fear and uncertainty among City firms.
Two major firms held emergency talks with partners the day that The Lawyer broke the story and two others - Slaughter and May and Cameron McKenna - are planning to issue memos to all staff reminding them of their obligations to report suspicious clients and financial transactions to police.
Robert Derry-Evans, managing partner at Cameron McKenna, said: "We have reporting procedures and we have detailed procedures for opening files and investigating new clients.
"I am intending to remind my staff all around the world of what their obligations are.
"It [money laundering] is something that is prevalent and City law firms are not immune. We just have to be on our guard."
Jonathan Haw, executive partner at Slaughter and May, said: "A memo will go out to all staff reminding them of the procedures."
He said Slaughter and May had strict guidelines and procedures in place to deal with suspicions about new clients and new business transactions.
A Law Society spokesman accused the police intelligence officer who revealed the investigations of "talking out of the back of his head".
However, Alistair Walters, a senior associate specialising in fraud and money laundering at Dibb Lupton Alsop, attacked the Law Society for its failure to treat the situation seriously.
He claimed that he was aware of several individuals involved in such activities. "You hear the same names coming up. Yet I don't think the Law Society ever does anything when I report names to them," he said.
Simon Goddard, in charge of NCIS' organised and economic crime unit, said the firms were actively working as fronts for gangs as diverse as the Russian mafia and Colombian drug cartels.
The profits from drug trafficking, gun running and contract killings were being laundered through London lawyers, who set up off-shore accounts and complex financial arrangements to disguise its origins, he said.
One senior partner with a top-ten law firm said: "You have stirred up a bloody hornets' nest. Obviously people have been talking about it in the firm. It's a bit of a horror story."
Law firms involved in commercial deals are required by law to comply with the Money Laundering Regulations 1994, introduced to combat organised crime. One of the requirements is that financial firms have Money Laundering Reporting Officers (MLRO).
Several big City firms spoken to all said an MLRO was in place.