The actress initially joked about the breakup rumours on a TV interview to promote her new film Café de Flore.
"People say we are buying houses in the middle of nowhere, or that we have fifty two houses in France," she said.
"And that is along with saying we split up every winter and get married every summer, and that I'm on my twelfth pregnancy.
"All that is not too serious, but this latest one is a rumour which could cause a lot of harm to my family and my children."
But the interviewer then asked her directly: "Why don't you respond to the rumour and put an end to it? Is the rumour false?"
Vanessa responded: "Yes, it's false - of course it's false."
The Joe Le Taxi singer has put the drama surrounding her personal life aside to continue on the promotional trail.
She was also at Paris Fashion Week looking elegant at the Chanel show in a floor-length white gown.
There are claims that Vanessa and Johnny, parents to Lily-Rose, 12, and Jack, nine are living separate lives and that their relationship has been on rocky ground for some time.