As it was unveiled, Indian air force planes showered it in flower petals.
The statue, which will be dedicated to the nation, has received opposition from some tribal groups in Narmada district.
Nehru's great-grandson, Rahul Gandhi, leads the Congress Party, and if a unified opposition wins a majority of seats in parliamentary elections due next spring, he could be a candidate for India's next prime minister.
The edifice is situated in Gujarat state, where both Prime Minister Narendra Modi and Patel hail from.
That makes the mega statue nearly 200 feet higher than the world's next largest, the Spring Temple Buddha in China, which stands at about 420 feet.
It was Modi who inaugurated the statue Wednesday morning.
The letter to Mr Modi said: "When we are still struggling to avail basic infrastructural facilities for schools, hospitals and drinking water, you decide to spend crores of rupees for the construction of a statue and now again for the inaugural event. Located by the banks of river Narmada, the height of this statue is twice that of America's renowned "Statue of Liberty", Prime Minister said in his Mann-Ki-Baat broadcast through All India Radio.
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An astonishing £330 million (Sh431 billion) has been spent on the 600ft tribute to Indian independence leader Sardar Vallabhbhai Patel in his home state of Gujarat. It is made up of almost 100,000 tonnes of concret and steel.
Sand animator Sudarsan Patnak also paid tribute to Sardar Vallabhbhai Patel on his 143rd birth anniversary with a sand art at Puri sea beach.
The BJP says Congress has deliberately ignored leaders such as Patel, B.R. Ambedkar, who led the drafting of the constitution, and freedom fighter Subhas Chandra Bose.
"They considered our diversity our biggest weakness but Sardar Patel converted this into our biggest strength". Mr Modi had laid the foundation stone of the project on 31st October 2013 when he was the Chief Minister of Gujarat.
The project also includes a memorial park at the base of the statue, a visitor facilitation centre and a reception desk.
Standing tall at Sadhu Bet Island on the Narmada River in Gujarat, the Statue of Unity is created to withstand winds, vibrations and natural disaster.