SM Krishna joined the BJP at a ceremony at the party headquarters in Delhi.

Highlights After 46 years in Congress, SM Krishna had quit the party in January

Today, he said India has progressed "because of PM Modi's leadership"

He said joining BJP was a 'very important step' in his onward journey

SM Krishna, one of the tallest Congress leaders in Karnataka who quit the party after 46 years in January, formally joined the BJP this afternoon at its headquarters in New Delhi. The veteran leader, who had said the Congress did not need him, described the step as "a very important stop in my onward journey".At the programme, attended by party chief Amit Shah and other key leaders of the BJP, he said India has progressed "because of the leadership of PM Modi and Amit Shah".One of the towering figures in the Congress, Mr Krishna's shift raises concerns about large-scale defection from the party's state unit as the Siddaramaiah government faces assembly elections next year. It is also a huge shot in the arm for the BJP, which, after seizing control of three of the seven north-eastern states, is looking for a foothold in the south.The 84-year-old had resigned from the Congress' primary membership, miffed that the party's state unit did not give him a key role or consulted him on key issues.A trusted aide of Indira Gandhi and Rajiv Gandhi, Mr Krishna, who served as Karnataka's Chief Minister between 1999 and 2004, is credited with setting up Bengaluru as the nation's IT hub. Later, he served as the Maharashtra Governor and even had a stint as the country's external affairs minister during the UPA government. Later, he returned to Karnataka, hoping to play a role in state politics.

A day after he quit Congress, Mr Krishna said the party did not need mass leaders any more. "I felt for some time that Congress doesn't need me, the party now depends on situation managers. They do not want time-tested leaders and workers," he had said. But he had made it clear that he was not considering retirement.Last month, the BJP's Karnataka chief BS Yeddyurappa had said Mr Krishna, who had decided to join the BJP, was unsure about the timing.