Vatican Radio has withdrawn an invitation to the head of Novartis to act as an external commentator after it discovered the Swiss drugmaker made contraceptives, the broadcaster said.

"The approach of the Vatican to artificial contraception cannot be subject to the smallest doubt," Vatican Radio said on its website.

The broadcaster had asked Novartis Chief Executive Daniel Vasella to be its "Commentator of the Week" in February, but said it had now decided to fill the slot internally.

"We ask Mr Vasella and our listeners to understand this decision. We have only just learnt from the press that Novartis also produces contraceptives," Vatican Radio said.

Novartis, which declined to comment, produces contraceptives at its generic drugs units.

The broadcaster said its commentator of the week did not necessarily have to express the Vatican's viewpoint.