The pair, who split in February 2007, sparked speculation after being spotted enjoying a "romantic" stroll in Paris together last week.
They were seen walking Martinez's dogs, shopping and enjoying drinks in a café the following day.
Reports claimed that Minogue had taken the French actor back after he agreed to marry and have a baby with her.
However, her spokesperson told Now: "The whole thing is made up."
The 39-year-old previously dismissed rumours of a reunion last October.