Italian police have been asked to investigate a case in which doctors treating a 40-year-old woman who was pregnant with twins aborted a healthy foetus while leaving a second, malformed one untouched.

The San Paolo hospital in Milan yesterday confirmed a report of the blunder in the daily Corriere della Sera. A statement from the hospital said the twins had changed places inside the womb between the first ultrasound scan and a second one carried out shortly before the operation, which took place in the 18th week of the pregnancy. It said it had handed the case notes to the "competent authorities".

The "misfortune", as the hospital termed it, is the latest of several high-profile errors that have prompted fierce debate over both the standards of professionalism in Italy's hospitals and the application of its abortion law. In March, a foetus aborted in the 22nd week of pregnancy at a hospital in Florence, because of suspected deformities, was found to be physically sound. It was rescuscitated and survived for a brief period.

A leading Christian Democrat politician, Luca Volonte, denounced the latest case as "infanticide arising from a contempt for human life". He said the health minister should also investigate the blunder, which the hospital said took place in June.

Italian news agencies said the woman subsequently returned to hospital to have the remaining, deformed foetus aborted. She then reported the doctors to police.

Italy's still-controversial 1978 law provides for abortion on demand up to the 90th day of gestation. However, doctors can terminate pregnancies at a later stage if there is a danger to the life of the mother or if the foetus is malformed.

In 2004, the latest year for which figures are available, less than 3% of the 138,000 abortions in Italy, were undertaken after the 90-day mark.