A former CIA case agent was sentenced on Friday to 19 years in prison, for an espionage conspiracy with China.

Jerry Chun Shing Lee, 55, was sentenced in federal court in Alexandria, Virginia, after his guilty plea to conspiracy to commit espionage.

Prosecutors and defense lawyers disagreed about the extent of the crime.

Prosecutors said Chinese intelligence officers gave Lee more than $840,000 (£655,000) and Lee probably gave them all the information he had from 13 years as a CIA case officer. They sought a prison term of more than 20 years.

Defense lawyers said the government never proved the money came from China or that Lee carried out any plans to deliver secrets. They sought a 10-year sentence.

Lee’s lawyers noted that Lee admitted that he agreed to engage in an espionage conspiracy with China, but never admitted that he actually divulged any secrets.

“What the government is describing is their worst possible nightmare,” said defense lawyer Nina Ginsberg.

Prosecutors acknowledged they had no direct evidence to prove what was transmitted, nor proof that the $840,000 Lee deposited into his bank account over a three-year period came from China.

But they said Lee was never able to come up with a good explanation. He ran a tobacco business in Hong Kong but it was essentially a failure, they said.

“The only logical conclusion,” said prosecutor Neil Hammerstorm, is that Chinese intelligence “must have been getting top-drawer, high-quality [information] from this defendant”.

Prosecutor Adam Small said the government believes Lee turned over information found in a notebook and USB drive as part of the government’s investigation. That included the names of eight CIA clandestine human sources, Small said, people Lee recruited and handled from 1994 to 2007.

Small said Chinese intelligence officers who met Lee gave him more than 20 “taskings” in which they sought details of CIA spycraft.

“Everything he knew would have been highly valuable to the PRC,” Small said.

Ginsberg said there was no evidence any of the sources identified in the notebook were harmed or compromised.

“I dare to say the government would certainly know if their agents had been exposed,” Ginsberg said.

Small countered that the risk of harm from Lee’s conduct was grave, and “whether something has or has not occurred is in some ways irrelevant”.

The biggest clue to the depth of Lee’s betrayal, prosecutors said, was the amount of money they said he received, which dwarfed what other spies have received.

Prosecutors pointed to the recent case of Kevin Mallory, a former CIA officer sentenced to 20 years for disclosing secrets to China in exchange for just $25,000 (£19,500).

“I take full responsibility for my conduct,” said Lee, a naturalized US citizen who immigrated to Hawaii from Hong Kong when he was 15.