A public housing tenant who laundered an average of HK$5.1 million each day over three years was told yesterday she will spend the next 10 years behind bars.

Lam Mei-ling, 61 - who was charged with laundering HK$6.8 billion in 39,000 transactions through nine Hong Kong banks between 2002 and 2005 - was found guilty by a High Court jury on Monday.

The judge noted it was the second- largest money laundering operation in Hong Kong's history. In January, a 22-year-old man was convicted of laundering HK$13 billion and sentenced to 10 and a half years in prison.

Justice Andrew Chan Hing-wai said yesterday he accepted that Lam was not the mastermind but there was no doubt she played an active role.

"The defendant's family background and personal matters are not a matter for leniency as placing a deterrent punishment on money laundering cases is the major consideration," the judge said.

When questioned by police, Lam frequently claimed she had forgotten and did not know things. This delayed the legal process, which was why Lam was not charged until four years after her arrest in 2008, the judge said.

During the trial, the court heard Lam received occasional monthly payments of just HK$4,500 - less than the minimum wage - for transferring the massive funds for a mainland friend.

But Justice Chan said Lam was not as ignorant as her lawyer claimed. She was fined HK$27,000 in 2002 for not keeping a record as a remittance agent and should have known her legal responsibility. Police seized a manual for foreign exchange agents, which mentioned money laundering, in her home at Choi Wan Estate, Ngau Chi Wan, Kowloon.

They uncovered the case only when investigating a deception claim by a Dutch man and found a HK$300,000 transaction in Lam's account.

A specialist on political and corporate risk said the recent prosecutions are not necessarily an indication of loopholes in the financial system but, rather, are the result of an increased crackdown in the mainland.

"Hong Kong is a free market," said Steve Vickers, chief executive officer of SVA Steve Vickers and Associates and a former commander in the Royal Hong Kong Police. "The scary part is the ease with which gaming money, illegal and otherwise, oozes out of China.

"The real loopholes are in the Chinese exchange controls. In the past 12 months the country has been literally hemorrhaging money, mostly through junket operators and underground banks.

"There is a crackdown on these now."

In January, Luo Juncheng was jailed after a jury convicted him of laundering a fortune through a Hong Kong bank over eight months, ending in 2010.

The case cast serious doubts on SAR safeguards against money laundering.