BOGUS Buddhist monks are scamming Perth shoppers for "donations" in return for plastic amulets.

Authorities are now investigating the robed conmen, who have been pestering people in busy Hay St Mall this week.

Perth users of the online forum Reddit posted warnings about "fake monks", claiming they were handing out gold-looking medallions and then asking for a donation.

"They also pull out a notepad suggesting that other people have donated anywhere from $20 to $50 claiming it goes towards a temple," one post read.

The Sunday Times this week watched as two men wandered through the mall dressed in orange cotton robes, one with matching pants, the other in jeans. Both wore running shoes.

When one was approached by The Sunday Times, he repeatedly asked for a donation before walking off.

One shopper said he was asked to donate $20, after having offered $5.

The Tibetan Buddhist Society and The Buddhist Society of WA said they did not send monks out to collect money.

Consumer Protection acting commissioner Gary Newcombe said it was the second time in two months there had been reports of fake monks scamming people for cash.

"This is a matter of concern," Mr Newcombe said.

"A permit is required from Consumer Protection to undertake street collections and these are usually limited to Fridays."

Consumer Protection will now talk with WA Police and the Australian Competition and Consumer Commission, which also regulates charities, to tackle the problem.

"Anyone being approached in the street by someone seeking a donation should ask to see evidence of their street collection permit," Mr Newcombe said.