It recorded 209 criminal acts per 1,000 residents in 2013, higher than any other city in the country, the federal statistics office said.
The rate was down three percent from 2012, when Lausanne also held the title for most per capita crimes, but figures showed rates dropping even more in other cities.
The capital of Vaud, ranked ahead of Bern, where 168 violations were recorded per 1,000 residents, six percent lower from the previous year.
Geneva followed (160, down 13 percent), ahead of Zurich (138, also a drop of 13 percent).
The overall number of criminal code infractions fell by six percent to 575,139, including an eight percent reduction in the number of thefts (217,978 in 2013).
The statistics office said there fewer break-ins and less violent acts, but more sex crimes.
The cases of pornography jumped by 68 percent, the office said.
Cases of fraud increased by 15 percent, while those of extortion and blackmail, also rose by 67 percent, while incidents of reported domestic violence dipped by four percent.
When drug infractions and violations of the law on foreigners were included, the total number of crimes in the country fell by three percent to 725,687.
The number of illegal drug infractions rose by five percent.
Illegal entries into the country, coupled with unauthorized stays, accounted in part for the 14 percent rise in foreigners law offences, the statistics office said.