Britain's advertising watchdog said Tuesday it was investigating a TV advert for Nurofen after some versions of the painkiller were removed from shelves in Australia over misleading claims.

The Advertising Standards Authority said it was investigating complaints that a Nurofen Express television advert was misleading as it implied muscles in the head were directly targeted by the drug, manufactured by Britain-based drug multinational Reckitt Benckiser.

Complainants also questioned whether the advert's claim that Nurofen Express worked faster than standard paracetamol or ibuprofen was misleading.

The watchdog said it had received 12 complaints about the television advert in February and launched an investigation in March.

"This is a complex case and our investigation is ongoing. The advertiser is providing evidence to substantiate its claims, we're carefully assessing that and we'll publish our findings in due course," a spokesman for the authority said.

It comes after an Australian court on Monday ordered Reckitt Benckiser to remove some of its Nurofen brands from shelves as it found they made misleading claims.

The Federal Court ruled that the company had engaged in misleading conduct as the in four products marketed as treatments for specific pain such as migraines and back pain was the same.