The era of coalition government began in India in?

1989

Elections in 1989 led to the defeat of the Congress party but did not result in a majority for any other party. Though the Congress was the largest party in the Lok Sabha, it did not have a clear majority and therefore, it decided to sit in the opposition. The National Front (which itself was an alliance of Janata Dal and some other regional parties) received support from two diametrically opposite political groups: the BJP and the Left Front. On this basis, the National Front formed a coalition government, but the BJP and the Left Front did not join in this government. Thus, from 1989, era of coalition started.