A letter marked "top secret and personal" reads: "The Indian authorities sought British advice over a plan to remove Sikh extremists from the Golden Temple."

British Prime Minister David Cameron has directed his Cabinet Secretary to establish the facts behind claims that Margaret Thatcher’s government may have helped Indira Gandhi plan Operation Blue Star in 1984.

Labour MP Tom Watson and Lord Indarjit Singh had demanded an explanation after recently declassified documents indicated that Britain’s Special Air Service (SAS) officials had been dispatched to help India on the planning on the raid of the Golden Temple to flush out militants from the shrine, an operation left more than 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 UK government spokesperson said in a statement issued in London on Monday night.

“The PM and the Foreign Secretary were unaware of these papers prior to publication. Any requests for advice from foreign governments are always evaluated carefully with full Ministerial oversight and appropriate legal advice,” he added.

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 letter marked “top secret and personal” dated February 23, 1984, nearly four months before the incident in Amritsar, titled ‘Sikh Community’, reads: “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.”

“These documents prove what Sikhs have suspected all along, that plans to invade the Golden Temple went back months even though the Indian government was claiming even weeks before that there were no such plans,” Lord Singh, also the director of the Network of Sikh Organisations in the UK, told PTI.

“I have already approached the Indian government through the High Commission of India for the need of an independent international enquiry to establish the exact facts. I will now raise the issue in the House of Lords,” he added.

Some of the documents have been reproduced on the ‘Stop Deportations’ blog which focuses on Britain’s immigration policy and claim Thatcher sent SAS officials to advise Mrs Gandhi on the operation.

“I’ve only seen the documents on Monday and am told there are others that have been withheld. This is not good enough. It is not unreasonable to ask for an explanation about the extent of British military collusion with the government of Indira Gandhi,” Mr. Watson, an MP for West Bromwich East, said.

He has written to UK foreign secretary William Hague and plans to raise the issue in the House of Commons.

“I think British Sikhs and all those concerned about human rights will want to know exactly the extent of Britain’s collusion with this period and this episode and will expect some answers from the Foreign Secretary,” he added.