Corbyn's letter to Downing Street, dated January 4, follows what he describes as "significant representations" from a wide range of representatives from the British Sikh community demanding details of the full extent of the UK's alleged role in the military action on Golden Temple in 1984.
"Given concerns regarding the effectiveness and integrity of the January 2014 review, I believe we must consider a fresh, independent investigation into this episode in British history.
In 2014, then Prime Minister David Cameron had ordered the Heywood Review into the exact nature of British involvement in theIndian Army operation at Golden Temple in June 1984 after documents released previously under the 30-year declassification rule had implied British SAS commanders had advised the Indian government as it drew up plansfor the removal of militants from the Sikh shrine.
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Corbyn's letter notes: "This review was felt by many to be inaccurate and the presentation of its conclusions to Parliament in February 2014 to be misleading. A valuable opportunity to bring greater transparency to this was lost with the recall of 33 FCO [Foreign & Commonwealth Office] India files from 1984, which had only been released late in August 2016 after 32 years (contrary to the 30-year rule).
"This recall came within a matter of weeks of the files being released, depriving those interested of the opportunity to fully review their contents - and sending a signal that the government is not committed to transparency."
(Reopens FGN 21)
Meanwhile, Sikh Federation UK welcomed the move with its chair Bhai Amrik Singh expressing his gratitude to Corbyn.
"We are grateful the Labour leader has written to Theresa May to call for a fresh, independent investigation and deliver the British public transparency. British Sikhs will continue to call for transparency and this can only be delivered through an independent investigation that has full access to all relevant papers," he said.