In a major political development, at least six of the seven Maharashtra Navnirman Sena corporators of BrihanMumbai Municipal Corporation (BMC) on Friday walked over to the rival Shiv Sena, official sources confirmed.

The group of six MNS corporators have sought permission of the Konkan Divisional Commissioner to be recognized as a separate group.

They are expected to support the Shiv Sena in the BMC, said a top MNS leader, though the party leadership has not reacted to the development.

The move comes as a major shock to Sena ally, Bharatiya Janata Party which on Thursday proclaimed that “very soon, a BJP Mayor would rule over the BMC”, after the party bagged the Bhandup ward in the civic by-elections on Thursday.

The MNS corporators who have switched sides are: Archana S. Bhalerao, Parmeshwar T. Kadam, Ashwini A. Matekar, Dattaram S. Narvankar, Harshala A. More and Dilip B. Lande.

Now, the sole MNS corporator left in the BMC is Sanjay R. Turde, whose moves were scuttled at the last minute for some unknown reasons.

Stunned by the sudden development, the BJP cried foul and hurled allegations of “horse-trading” by lodging complaints with the Maharashtra State Election Commission, Maharashtra Anti-Corruption Bureau and the Konkan Development Commissioner.

Bouyed by Thursday’s victory in the Bhandup civic by-poll, BJP MP Kirit Somaiya had declared that now the Shiv Sena had 84 corporators and the BJP 83.

“Very soon, the BJP will become 84 and our Mayor will be appointed,” Somaiya had predicted, sending jitters in the Shiv Sena.

According to sources, the Sena burnt the midnight oil to work out its political strategy to avert the possibility of losing its control over the country’s richest municipal body, with Mayor Vishwanath Mahadeshwar playing a key role in weaning away the MNS corporators.

In the 227-member BMC, the current party-wise position is: Shiv Sena 84 and four independents, BJP 83 and two independents, Congress 30, Nationalist Congress Party nine, MNS seven, Samajwadi Party six and All India Majlis-e-Ittehadul Muslimeen (AIMIM) two corporators.