In an interview on Wednesday with Rundschau, a current affairs programme from state broadcaster SRF, Varoufakis complained of the difficulty in tracking down tax dodgers.
“Sometimes we know that someone has taken money away from Greece,” he told the programme.
“But we do not know in what city or which bank it is located in Switzerland,” Varoufakis said.
The finance minister, a key player in the Greek government as it struggles to reach an agreement with the European Union to finance its debt, said it was impossible to obtain such information from Swiss authorities.
“We know too little to be able to locate the black money.”
But Varoufakis said the Greek government is working on a plan to allow tax evaders to voluntarily disclose their situation and invest their assets in Greece while paying a penalty of around 22 percent.
“if you set the taxes too high, it does not work,” he told Rundschau.
If the rates are too low, there is a problem with justice not being met, Varoufakis said.
“It's never easy finding a middle ground.”
SRF reported that experts believe wealthy Greeks may have socked away as much as €80 billion in Swiss banks.
Varoufakis said he did not want to speculate on the amount involved.
“It's like being at an archeological dig,” he said.
“Before you dig you do not know what you will find.”
Swiss authorities contest the suggestion that they are not cooperative in tracking untaxed assets.
An official for the state secretariat for international financial matters said that Switzerland had made proposals to Greece for some time and was willing to make “better use of existing laws” to help out.
Varoufakis acknowledged that Greece has had a problem with tax collection, noting, for example that the islands of Santorini and Mykonos last year had twice as many tourists as the previous year yet tax receipts had fallen from the islands had fallen by 20 to 30 percent.
If Greece does not receive a fresh infusion of capital this month it faces national bankruptcy.
But Varoufakis warned that a Grexit (Greek exit from the euozone) would have a negative impact on Switzerland.
“The last things you need in Switzerland is additional capital flight,” he said.