The last opportunity to avoid the partition of India was lost with the rejection of

The Cabinet Mission Plan of 1946 represented the last viable compromise that could have preserved a united India by creating a limited Union handling defence, foreign affairs and communications while leaving provinces and states wide autonomy; it envisaged optional provincial grouping and a single Constituent Assembly, a formula that both major parties initially engaged with [2]. The failure to implement and eventual rejection of the Cabinet Mission proposals removed that negotiated middle path and made a federal settlement increasingly unattainable, turning 1946 into the decisive year after which partition became inevitable [3]. Thus the last opportunity to avoid partition was lost with the rejection of the Cabinet Mission.

Sources

1. [1] History , class XII (Tamilnadu state board 2024 ed.) > Chapter 7: Last Phase of Indian National Movement > Cabinet Mission > p. 93
2. [2] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 25: Independence with Partition > Why Congress Accepted Partition > p. 499
3. [3] https://frontline.thehindu.com/other/article30245572.ece