Delta Goodrem has a hidden relationship with one of her team members on The ...

The Voice's Natasha Stuart told Boy George after her blind audition she once performed with him before her cancer treatment.

But the 42-year-old songstress also has a history with her mentor Delta Goodrem which has been made much less clear. 

Natasha sung backing vocals for Delta shortly after her 2003 battle with Hodgkin's Lymphoma which has raised the question of whether the contestant has an unfair advantage. 

Keeping it quiet: The Voice songstress Natasha Stuart, 42, has a history with her mentor Delta Goodrem (pictured)

Keeping it quiet: The Voice songstress Natasha Stuart, 42, has a history with her mentor Delta Goodrem (pictured)

The band singer has also supported Guy Sebastian, meaning she has provided her vocals to three of the four mentors on The Voice.

The connection between Delta and Natasha has grown stronger each week, with the Australian household name supporting her on the piano in the knockout round, in what was a world first for the show. 

Speaking to 9Honey last month Natasha, who finished 20 weeks of chemotherapy for breast cancer in January, said Delta was the obvious choice to be her mentor.

Connection: Natasha sung backing vocals for Delta shortly after her 2003 battle with Hodgkin's Lymphoma

Connection: Natasha sung backing vocals for Delta shortly after her 2003 battle with Hodgkin's Lymphoma

'In that moment it just felt like she was a kindred spirit and I had to go with her,' she said. 

'Everything Delta said to me just connected so deeply to where I'm at now and what I'm going through, and what I know she's gone through.' 

Last week, Natasha reduced Kelly Rowland and Delta to tears during her victorious knockout-round performance of REM's Everybody Hurts on The Voice.

Making history: The connection between Delta and Natasha has grown stronger each week, with the Australian household name supporting her on the piano in the knockout round, in what was a world first for the show

Making history: The connection between Delta and Natasha has grown stronger each week, with the Australian

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