Unusual reason fans are throwing bras and underwear at Delta ...

Delta Goodrem has spilled on the reason female fans are now throwing bras and underwear at her while on stage.

The popular Australian singer-songwriter performed in Bowral over the weekend and was left stunned to be collecting undergarments mid-performance.

WATCH THE VIDEO ABOVE: Delta Goodrem on Sunrise.

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She teased the audience by sharing that it was her “lucky day” when the first bra was thrown by an excited concertgoer.

“I’ve got a bra, I’ve got some knickers, fantastic! This is my lucky day, never at one of my concerts have I had a bra thrown at me,” she said.

The singer swung the undergarment in the air as a prop during her cover of The Pointer Sister’s song I’m So Excited.

Goodrem spoke out about the performance on Tuesday, insisting that the act was because she was performing during a Tom Jones performance.

Jones, 83, had a loyal group of female fans known to throw their underwear on stage during his peak in the 1960s — this tradition has continued to this day.

“Yeah, well, it’s a Tom Jones concert. So it was part of us together. The two of us ... we’re doing a Day On The Green together,” Goodrem told Sunrise.

“Frankly, I wanted to start the spirit, I heard that’s what everyone was doing. In my wildest dreams, I never thought in my career I’d start having knickers and bras, but we had so much fun!

“It was awesome.”

She joked of the “Tom Jones effect” that the “touch has been passed on! It’s gone to me!”

WATCH THE VIDEO BELOW: Delta Goodrem has bras thrown at her on stage.

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After the performance on the weekend, Goodrem revelled in the moment.

“You think you’ve done so much a couple of decades into performing live, and then you get your first bra thrown on stage, and it’s a new standard unlocked ????… ????????” she captioned an Instagram photo.

Fans and friends reacted to the unexpected moment.

One of the culprits wrote on Instagram: “Hahahahaaa!!!!! I threw you the pink undies ... they were not mine, some lady threw them at me! So I passed them along to you.”

“Come for the show, stay for the wardrobe upgrade ????,” media personality Rove McManus wrote.

“From now on, bras at every show ????????,” The Delta Museum account said.

“So glad I was there to witness this first! It was hilarious, ????????,” another commented.