The Scots performer will be brought in on Saturday to beef up the panel of experts on the BBC1 show – launched in direct competition to ITV's The Voice – when it swings into its second phase, known as The Collaboration Stage.
Lulu, 68, said: "You want the full package from everybody. I'm sorry but that's what you have to have these days, you can't just be a singer or just a dancer or just cute. There is so much competition out there."
The star, widely known for her 1969 Eurovision Song Contest winning entry Boom Bang-a-Bang, and in the UK for her 1964 hit Shout, teams up with old pal Gary Barlow for the show's bid to discover five nobodies to join the brand new Take That musical The Band.
Lulu will make an appearance on Let It Shine on Saturday
Having collaborated with the group on 1993 hit Relight My Fire, she commented: "There are absolutely no jokes on this show. No way. I'm both impressed and surprised. It's exciting."
She also cautioned the acts who have made it past the Starway stage: "If you get turned down now, it's not personal. That's something you have to contemplate no matter what your age, rejection will either make you or break you. What doesn't kill you will make you stronger.
"I've had so many disappointments in my life, if I had let one of them breakme I wouldn't be here today."
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Apple Tree Yard starring Emily Watson and Ben Chaplin, contained a number of sex scenes – including a traumatic rape scene
Lulu sent out a warning to contestants who might worry about being dropped
On a personal note, she added: "I didn't do what I did to be famous. I think that separates the chaff from the wheat. It's a tough business to be in, especially when you get knocks, so the easiest thing would be to probably say, 'Ah, stuff it'. But the ones who aren't in it for the fame won't do that. They keep going, regardless of the knock-backs."
I didn't do what I did to be famous. I think that separates the chaff from the wheat
The second stage of the competition sees the hopefuls put into five groups of eight, with each group performing with guest acts such as Busted, Kaiser Chiefs, Beverley Knight, Olly Murs and Melanie C.
Five singers from each group will make it through to the live shows, all competing to join The Band, which will begin rehearsals in July before hitting the road and touring nationwide.