"If any senior leader from the BJP supports either Maharashtra Navnirman Sena chief Raj Thackeray or Nationalist Congress Party (NCP) leader Sharad Pawar, it can affect the 'mahayuti' (grand alliance)," Sena spokesperson and MP Sanjay Raut said.
He was reacting to reports that the Shiv Sena was peeved over Monday's meeting between BJP leader Nitin Gadkari and Raj Thackeray, sparking speculation that the BJP was trying to woo the MNS.
However, Gadkari dismissed the Sena's apprehensions, saying he only discussed strategies to dislodge the Congress in the Lok Sabha election.
Not convinced, Raut said: "The Marathi votes will always be with the Shiv Sena and nobody can take it away."
Meanwhile, Republican Party of India-Athawale chief Ramdas Athawale, which is part of the alliance, said it would welcome the MNS into the NDA.
Shiv Sena supremo Uddhav Thackeray is said to be displeased over the BJP-MNS links. State BJP chief Devendra Fadnavis rushed to meet him at his bungalow around midnight.
Uddhav Thackeray said there was a "communication gap within the BJP" as its leaders speak of defeating the Congress-NCP government but keep praising Pawar or Raj Thackeray.
At their meeting Monday, Gadkari reportedly urged the MNS not to put up candidates in the Lok Sabha election and instead support BJP candidates to oust the Congress-NCP combine.