The April 13, 1919 Jallianwala Bagh massacre, in which British troops opened fire on thousands of unarmed protesters, remains an enduring scar of British colonial rule in India.
Colonial-era records show about 400 people died when soldiers opened fire on men, women and children in an enclosed area, but Indian figures put the toll at closer to 1,000.
Former British prime minister David Cameron described it as "deeply shameful" in a visit to the northern Indian city in 2013 but stopped short of an apology.
In 1997, Queen Elizabeth II laid a wreath at the site but her husband Prince Philip stole the headlines by reportedly saying that Indian estimates for the death count were "vastly exaggerated".
Nirmala Sitharaman, India's defence minister said that now was the time for Britain to say sorry.
"Without a doubt, yes," Sitharaman said. "There couldn't have been a bitterer tragedy during the freedom movement in India.... That was an inhuman act."
Arguments that apologising would leave London open to legal claims "could be no legitimate reason to say I shall not regret this. That's the baggage you have to carry with you."
Sitharaman also said that Britain should also say sorry for a lesser-known but much bigger tragedy -- the Bengal famine in eastern India during World War II.
As many as three million people died in 1943 after Japan captured neighbouring Burma -- a major source of rice imports -- and British colonial rulers in India stockpiled food for soldiers and war workers.
"Three million people, they starved to death... Britain owes an apology for that," she said.
"That was a man-made disaster. Grains of Bengal, from all parts of India, were all diverted for the war, depleting the people's basic needs."
Sitharaman added that the chaos over Brexit was "really sad".
"It is a situation in which no country would ever want to be in, because it is an unenviable position. You have thrown yourself into an area about which you have no clue."
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