The US Food and Drug Administration says there is no need for an urgent review of the safety of aspartame, despite a new study showing the sweetener may cause cancer.

A US consumer group has called for the review after Italian researchers published a new study that showed aspartame - widely used in soft drinks - might cause leukaemia, lymphoma and breast cancer in rats.

"This is the second study by the same lab showing that aspartame causes cancer in rats," Centre for Science in the Public Interest executive director Michael Jacobson said.