It was recently revealed that Mel B, Emma Bunton, and Geri Horner – formerly known as Geri Halliwell – are planning a concert and new material to celebrate the 20th anniversary of the Spice Girls’ debut single Wannabe.

Victoria Beckham and Mel C, however, will not be taking part.

And now, speaking in a revealing new interview with Event magazine, Melanie Chisholm has explained that her decision stemmed from a desire to protect her mental health.

The 42-year-old said: “When the Spice Girls were at their biggest, I couldn’t even really look at myself in the mirror because I didn’t like what I saw.

“Depression, eating disorders, obsessive over-exercising; I went through all of it.”

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The single mother went on to explain that she was offered £2 million to get involved with the upcoming Spice Girls reunion.

However, despite being tempted by the sheer amount of money on offer, the original Sporty Spice eventually decided to turn them down: her mental health had to come first.

“I’d like to say the money didn’t matter to me. I’m a single mother and I do have financial concerns,” she said.

“It was a really difficult decision. I didn’t take it lightly. I did go quite far down the route with the girls. I went to a lot of meetings but I just didn’t feel it was right in my gut.

“When I finally said no I just felt relief.”

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Mel C added: “‘Part of me will be Sporty Spice until I die. We had one reunion [in 2007] and I didn’t want to do that. But I was talked round and it was the right thing to do, we had a great time and then we played at the closing ceremony for the Olympics in 2012.

“That to me was where [the Spice Girls] should have been laid to rest. Sometimes you just have to say no.”

Beckham – aka Posh Spice - has yet to speak publicly about her own decisions for turning down the Spice Girls reunion offer.

However, speaking to James Corden on The Late Late Show earlier this month, Mel B said that she believed it had a lot to do with the businesswoman’s work with her fashion line.

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“You know, Victoria is busy with her great fashion line. Mel C is doing her own album.

“They gracefully said, ‘you three go ahead and do it’. We are girl power and we support each other so us three went, OK, well then let’s us three do it."

Despite this, there will be five women on the stage when the Spice Girls take to Hyde Park in July 2016 – although only three of them will be from the original line-up.

Scary, Ginger and Baby Spice are working together with the BBC to launch a new talent show, which will help them launch a nationwide audition process.

They will then, in live televised shows, sit down and judge the wannabe Spice Girls – and eventually pick two to join them for their reunion.

“I don’t think we could ever replace [Mel C and Victoria Beckham],” said Mel B, “but I’d like to invite other people to sing with us.”

The show is expected to kick off next April.