More than 400 documents, including government files relating to the UK’s involvement in Israel’s alleged nuclear arsenal, have gone missing over the last four years, it has been revealed.

The response to a Freedom of Information request showed the UK’s National Archive at Kew contains more than 11 million documents in total, including many government documents that become publicly available after 30 years.

Notable missing files include 1970s documents on nuclear collaboration with Israel, as well as a letter from Winston Churchill.

The losses include more than 60 Foreign office files, over 40 Home office documents, and six from the records of former prime ministers. 

According to the BBC, one MP from the parliamentary group on official archives said he was “concerned” by their loss. 

The losses were revealed by a FoI request submitted by the BBC.

A 1979 document titled “Military and nuclear collaboration with Israel: Israeli nuclear armament”, is among the missing pieces.

The file, contained among government files on arms control and disarmament in the 1970s, apparently relates to a United Nations resolution from 1978 which concerned “increasing evidence” Israel was attempting to acquire nuclear weapons.

Since the 1950s, Israel has retained a policy of nuclear ambiguity, neither publicly confirming nor denying whether it has a nuclear arsenal.  

However, Israel is now thought to possess 80 nuclear warheads, built up as western governments have “played along with the policy of ‘opacity’”, as the Guardian’s Julian Borger puts it. 

Labour MP Tristram Hunt, the vice-chair of the All-Party Parliamentary Group on Archives and History, told the BBC the missing files were a “worring loss”, but added that the National Archives were among the world’s best and were run “incredibly effectively and efficiently”. 

He said: “The challenge is to ensure that you've got the systems to prevent that, because with every loss of a potential piece of archive you're losing some history and understanding.