Theresa May on Wednesday described the Jallianwala Bagh massacre in Amritsar as a "shameful scar" on British Indian history but stopped short of a formal apology sought by a cross-section of Parliament in previous debates.

In a statement, marking the 100th anniversary of the massacre, at the start of her weekly Prime Minister's Questions in the House of Commons, she reiterated the "regret" already expressed by the British Government.

The massacre took place in Jallianwala Bagh in Amritsar on Baisakhi in April 1919 when the British Indian Army troops, under the command of Colonel Reginald Dyer, fired machine guns at a crowd of people holding a pro-independence demonstration.

According to the British government records, 379 people, including men, women and children were killed and around 1200 injured in the firing.

"The tragedy of Jallianwala Bagh of 1919 is a shameful scar on British Indian history. As Her Majesty the Queen (Elizabeth II) said before visiting Jallianwala Bagh in 1997, it is a distressing example of our past history with India," she said in her statement.

"We deeply regret what happened and the suffering caused. I am pleased that today the UK-India relationship is one of collaboration, partnership, prosperity and security. Indian diaspora make an enormous contribution to British society and I am sure the whole House wishes to see the UK's relationship with India continue to flourish," she said.

In response, Opposition Labour Party Leader Jeremy Corbyn demanded that those who lost their lives in the massacre deserve a "full, clear and unequivocal apology for what took place".

May's statement comes a day after British MPs at Westminster Hall of the Parliament complex debated the issue of a formal apology for the April 13, 1919 massacre to mark its centenary this Saturday.

Foreign Office Minister Mark Field had told MPs that he had been "compelled" by the arguments to raise the issue of going further than the "deepest regret" expressed over the killings during the British Raj.

"I feel that we perhaps need to go further... I have now been persuaded - not just by this debate - to take a different approach," the minister said, adding that the government had to also consider the "financial implications" of any apology for events of the past.

"These issues are an important way of trying to draw a line under the past. Therefore, this is work in progress and I cannot make any promises," he said, holding out some hope of a formal apology over the incident.