Bachchan, 72, who also read out an excerpt from Gandhi's 'The World of Tomorrow', took to Twitter to share his excitement.
"A historic moment and a historic presence... I am honoured and humbled. The unveiling of the statue of Mahatma Gandhi at Parliament Square, London, and invited to read from his work.
"At the unveiling the respect and dignity given... So humbling. David Cameron, Arun Jaitley, Gopal Gandhi and self on stage! Honour," Bachchan tweeted.
"My 4th visit to historic 10, Downing Street... The meeting with the PM of GB, and walking with him and other dignitaries to event! Walking through the portals of the Foreign Office of the Commonwealth, once the largest power house of the World ! Incredible feel," he wrote.
Gandhi's statue joins the figures of many prominent world leaders at London's Parliament Square like former British prime minister Winston Churchill and anti-apartheid icon Nelson Mandela.