CANBERRA (Reuters) - An Australian pub offering free drinks to women who remove their underwear and display it to patrons and staff will be investigated by alcohol licensing regulators, authorities said on Thursday.

The Saint Hotel in Melbourne has promised a "No Undie Sundie" event over the coming weekend, where woman who remove their underwear and hang it above the bar will receive A$50 (S$57) worth of free drinks.

Women who flash their bras and underwear to staff also get free drinks, the pub said, in a promotion that women's protection groups said was "almost an invitation to sexual assault".

"On the face of it, it looks like an inappropriate liquor promotion and we will be investigating with a view to banning it," Liquor Licensing Victoria director Sue Maclellan told the Herald Sun newspaper.

On its website the Saint describes itself as "the home of Melbourne's fashionable set", but pub attracted the ire of regulators in June after hiring a dwarf to pour free liquor down patrons' throats.

Posters for the no undies day event showed singer Britney Spears partially exposed and exiting a car in a scene local Mayor Janet Cribbes said was "bordering on being pornographic".

The pub's managers had gone to ground on Thursday and were not answering phone calls.

(Reporting by Rob Taylor; Editing by David Fox)

Photo: A model presents a creation as part of the Ultra collection during the Paris International lingerie show January 24, 2008.