In a significant development on Saturday, Lok Sabha Speaker Om Birla accepted the merger of six Shiv Sena (Uddhav Balasaheb Thackeray) MPs with the Shiv Sena faction led by Maharashtra Deputy CM Eknath Shinde.Birla formalised the long-anticipated merger, reducing the strength of the Uddhav Thackeray-led party in the Lok Sabha to just three MPs. The Shinde-led Shiv Sena, meanwhile, now has 13 MPs, up from its original strength of seven.With the merger today, Shiv Sena has become the third largest NDA constituent after BJP (239 MPs), TDP (16 MPs) and Shiv Sena (13 MPs). Shiv Sena has overtaken Nitish Kumar’s JDU in the NDA power pie. JDU has 12 MPs.The immediate impact of the move is reflected in the Lok Sabha’s composition, with the BJP-led National Democratic Alliance (NDA) increasing its strength to 298 in the 543-member House. Owing to three vacancies, however, the effective strength of the Lok Sabha currently stands at 540.The development comes as a boost for the NDA ahead of the Monsoon Session of Parliament, which begins on Monday, as the ruling alliance seeks to bolster support for key legislation, including potential constitutional amendment Bills.A two-thirds majority in a House with an effective strength of 540 requires the support of 360 MPs, leaving the NDA well short of that mark despite the latest addition to its numbers.Meanwhile, another petition pending before Birla concerns a request by 20 rebel Trinamool Congress MPs seeking recognition of their merger with the Nationalist Citizens Party of India (NCPI) and permission to function as a separate bloc supporting the NDA.While the proposed merger has not yet been formally recognised, Birla has allowed the 20 rebel MPs to sit separately from their former Trinamool Congress colleagues, including Diamond Harbour MP Abhishek Banerjee, nephew of Mamata Banerjee. If the group of 20 MPs is eventually recognised as a separate bloc aligned with the NDA, the alliance’s strength in the Lok Sabha would rise to 318.