The "Two Forms (Divided Circle)" sculpture was insured for 500,000 pounds ($776,000) and had been erected in Dulwich Park in 1970.
On Tuesday, the local authority, Southwark Council, offered a 1,000-pound reward for information leading to conviction of the thieves.
"It comes as soaring prices for copper, lead and bronze has meant that everything from railway lines, phone lines and even war memorials have been targeted by thieves across the country in recent years," the Council said in a statement.
Police are investigating the theft which took place overnight on Monday after thieves broke into the locked park, drove up to the statue and removed it.
"The theft of public art and metal is becoming a sickening epidemic," said Peter John, Leader of Southwark Council.
Just 24 hours earlier, London police had launched a dedicated team to tackle the growing problem of metal theft.
A Scotland Yard spokesman told Reuters: "An allegation of the theft of a sculpture has been received and investigations are on-going."
Source: Reuters Life! Online Report