There were 703 attacks on NHS staff in Cumbria and North Lancashire last year - but just 13 cases led to criminal sanctions.
The figures show the number of recorded assaults against doctors and nurses at the Morecambe Bay NHS Trust; the Cumbria Partnership NHS Trust; and the North Cumbria Hospitals NHS Trust.
South Lakes MP Tim Farron says it's a "shocking" level of violence and has called for stronger action to protect staff.
The Lib Dem leader says the government should adopt a zero tolerance approach to the issue, which would result in more prosecutions.
Mr. Farron said: “These figures are extremely concerning. Our dedicated doctors and nurses work incredibly hard to look after patients, and should never be expected to suffer an assault at work.
“No member of staff should come to work in the NHS and be subjected to, or even fear, assault. The government must take stronger action to protect NHS staff, and send out the message that there will be zero tolerance for violence against doctors and nurses.
“I am particularly concerned that this increase could be due, in part, to increased waiting times and an NHS which is struggling to cope with greater demands and less funding than is needed.”