Rihanna has been accused of slurring her words on stage at the opening show of her Australian tour. The pop star launched her Diamonds shows in Perth on Tuesday night (24Sep13) but the gig got off to a bad start as she left the audience waiting for more than 40 minutes before finally taking to the stage at the Perth Arena. A number of reviewers also claim the Umbrella star slurred her words while performing her hits, alleging she also showed "disinterest" and left most of the vocals to her backing singers. Jillian McHugh of WAtoday.com.au writes, "I wanted to be impressed with the two-hour show put on by Rihanna for the Australian premiere of her Diamonds World Tour, but I just wasn't... Bored and restless fans had waited inside the Perth Arena for her to take the stage... More than 40 minutes late... While slurring marked the first half of the show, it was her disinterest in singing along to more than half the words of each song that marked the second half. Largely carried by her back-up singers and backing tracks, she danced across stage with or without her microphone at her mouth, to much the same effect." Ashlee Mullany of the Sydney Daily Telegraph criticised the raunchier elements of Rihanna's show, writing, "(She) veered dangerously into X-rated territory. A barely there outfit, bottom suggestively stuck in the air and a bit of faux masturbation were all thrown into the mix." The bad reviews come just days after Rihanna was criticised for lip-syncing and forgetting her words at a post-Formula 1 Grand Prix concert in Singapore on Sunday (22Sep13). A Channel NewsAsia presenter, who was covering the gig, wrote in a series of posts on his Twitter.com page, "Spoiler alert: Rihanna is lip-syncing. From the ex-soundman next to me. Plus red light isn't on, on her mic... Am sure Rihanna just forgot the words and mouthed 'sorry'. At least she's singing (some of it). Dipping in and out of a backing track at least... Sounded & looked like she was in and out with a backing track helping out. Sang the slower ones though... Didn't she seem a little off her game? She did to me." Rihanna will perform in Adelaide, Brisbane and Melbourne before wrapping up her tour in Sydney on 4 October (13).