The singer, 48, said that she ‘wouldn’t be comfortable’ accepting money to take to the stage in the Gulf State, which is hosting the World Cup, due to its controversial human rights record.
Beckham accepted the lucrative deal despite public protest against the country’s laws against LGBTQ+ people and its often inhumane treatment of migrant workers and women.
Mel C, who recently won the honorary gay award at the Attitude Awards, told the Daily Mail: "Personally, I’m an ally to the LGBTQ+ community and it’s not something I would feel comfortable in doing.
"People want to go over there and help to make a change.
"Each to their own, but it would be a no from me if the offer came."
The star previously slammed Fifa’s decision to host the World Cup in Qatar as being all about "greed".
"They can try and spin it that they’re there to make change, that sport can make change. But it’s bulls**t, it’s about money," she told Attitude.
Mel’s comments could also put at risk her hopes for Victoria Beckham to reunite with the Spice Girls if they headline Glastonbury next year.
When asked previously if the girl group would play the festival together, she told ITV’s Lorraine: “I know Mrs Beckham would love to do it.”
She added: "I know it’s been rumoured a lot, it’s never been seriously talked about. But we do constantly talk about getting back on stage … I’m not saying it’s going to happen, but we’d love to”.
A spokesman for David Beckham has defended his association with the Qatar World Cup, telling Metro: "David has been visiting Qatar regularly for over a decade and went on to play for PSG [Paris Saint-Germain].
"He has seen the passion for football in the country and the long-term commitment that’s been made to hosting the World Cup and delivering a lasting legacy for the region."