Operations in which patients had the wrong body parts operated on have risen by a half in the last three years, claim figures show.
Wrong body part op claims are rising
Last year, 40 patients in England had claims settled by the NHS Litigation Authority - up from 27 in 2003-4. The cost of settling the claims topped £1m.
Among the mistakes were cases of the wrong leg and hips being operated on.
Campaigners said the errors were "unforgivable" and should never happen.
The data was released by the NHS Litigation Authority after a Freedom of Information request.
There were 27 claims settled for what is known as "wrong site surgery" in 2003-4, rising to 35 the following financial year and 40 in 2005-6.
Over the period, the cost of settling those claims, including damages and costs, increased from £447,694 in 2003-4 to £663,145 the following year and £1,098,975 last year.
A third of claims involved surgery on the wrong tooth, but wrong hips, knees and legs were also operated on.
Peter Walsh, chief executive of Action Against Medical Accidents, said: "These are accidents that should not be happening.
"This is not rocket science. It is all about having the correct procedures in place, it is not like we are talking about risk surgery.
"This mistakes have devastating impact on patients and is unforgivable."
A Department of Health spokeswoman said: "Millions of surgical procedures are carried out safely and correctly every day in the NHS and only a tiny number of cases are ever performed incorrectly.
"But the government is very clear, NHS patients who are injured as a result of clinical negligence should receive correct and full compensation."
And she added last year guidance was issued to doctors to ensure consistent methods were used to mark which body parts were due to be operated on.