The Shiv Sena on Saturday approached the Supreme Court against the 'arbitrary and malafide actions/decisions' of Maharashtra governor Bhagat Singh Koshyari in swearing in BJP leader Devendra Fadnavis as the chief minister.

The party has filed a writ petition in the apex court against the state governor, a Sena functionary said in Mumbai.

Early in the morning, Fadnavis was sworn in as the state chief minister and NCP's Ajit Pawar as his deputy. The political twist stunned the Sena and the Congress that together with the NCP chieftain Sharad Pawar had endorsed Uddhav Thackeray for the top job late last night.

The development comes hours after the Shiv Sena, NCP and Congress went through protracted negotiations to form a new coalition government with Sharad Pawar saying there was 'unanimity' over Uddhav Thackeray as chief minister.

The NCP chief later clarified that the decision was solely Ajit's and not the party's. Pawar said the decision of his nephew to join hands with the BJP was an act of indiscipline and attracts provisions of anti-defection law.

'Ajit Pawar's decision is an act of indiscipline. No NCP worker is in favour of the NCP-BJP government. NCP MLAs who support the BJP should know this move attracts provisions of anti-defection law,' he said, adding 10-11 MLAs had gone with Ajit to the Raj Bhavan.

He said the 54 newly-elected legislators of the NCP had signed a paper along with their names and constituencies for internal purpose and these signatures may have been misused as letter of support and submitted to the governor.

The NCP chief said that the MLAs were taken to the Raj Bhavan for oath-taking without their knowledge, adding that they have contacted him and informed how they were misled.

At least seven legislators claimed to have returned to the party fold and pledged their loyalty to Sharad Pawar.

Dilip Bankar and Manikrao Kokate, the MLAs from Nashik district, tweeted separately saying they were kept in dark about the oath-taking ceremony.

At the morning 'coup', Shiv Sena chief Uddhav Thackeray said, 'Earlier the EVM khel (game) was going on and now this is the new khel. From here onwards, I don't think elections are even needed. It is a repeated game by the BJP in every state.'

The Congress too has condemned the move, saying the 'clandestine' manner in which Fadnavis was sworn in as the chief minister will be written in black ink in the history of the state.