Cameron asked Cabinet Secretary Jeremy Heywood to conduct the investigation after documents declassified under the 30-year rule suggested a British special forces officer advised the Indians on carrying out the attack.
The premier's spokesman said the investigation will examine two issues - British action in 1984 and the decision to release such sensitive government papers.
Labour MP Tom Watson and Lord Indarjit Singh had demanded an explanation after documents made public over the New Year indicated that an officer of Britain's Special Air Service (SAS) was dispatched to help India plan for the raid on the Golden Temple, an operation that left over 1,000 people dead.
"These events led to a tragic loss of life and we understand the very legitimate concerns that these papers will raise. The Prime Minister has asked the Cabinet Secretary to look into this case urgently and establish the facts," a government spokesman said.
"The PM and the Foreign Secretary were unaware of these papers prior to publication. Any requests today for advice from foreign governments are always evaluated carefully with full Ministerial oversight and appropriate legal advice."
The documents being referenced were released by the National Archives in London under the 30-year declassification rule as part of a series over the New Year.
A "top secret and personal" letter, dated February 23, 1984, nearly four months before the raid in Amritsar, and titled "Sikh Community", stated: "The Indian authorities recently sought British advice over a plan to remove Sikh extremists from the Golden Temple in Amritsar.
"The Foreign Secretary decided to respond favourably to the Indian request and, with the Prime Minister's agreement, an SAD (sic) officer has visited India and drawn up a plan which has been approved by Mrs Gandhi. The Foreign Secretary believes that the Indian Government may put the plan into operation shortly."


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