"The comments are frivolous and shouldn't be taken seriously. Neither Mumbai nor Vidarbha will be separated from Maharashtra," the chief minister said.
"Unity is our strength," he said.
Meanwhile, Shiv Sena activists held protests outside De's house in South Mumbai on Thursday.
In the wake of the bifurcation of Andhra Pradesh, De had tweeted, "Maharashtra and Mumbai??? Why not? Mumbai has always fancied itself as an independent entity, anyway. This game has countless possibilities".
The tweet has raised the hackles of Shiv Sena and the Raj Thackeray-led Maharashtra Navnirman Sena.
While Shiv Sena leader Sanjay Raut demanded criminal action against De, Raj Thackeray launched a personal attack against the noted columnist.
De has refused to apologise or withdraw her comments.
India's vote lab set to cook up a chaotic 2014
Telangana bytes: 'A decision too late'
What may happen if India voted TODAY!
Re 1 to Rs 12 meals: These politicians should EAT their words!
Shah Rukh basks under Casablanca sun