An FBI file has revealed a potential plot to assassinate Britain’s Queen Elizabeth II during a visit to the United States in 1983.

The document, available on the FBI’s online vault, outlines what appears to be intelligence provided to federal agents about an IRA threat to the Queen’s life in California.

The Queen and her husband, the Duke of Edinburgh, made an official visit to the west coast of America in February and March 1983.

The file states that a phone call was made by “a man who claimed that his daughter had been killed in Northern Ireland by a rubber bullet”.

“This man additionally claimed that he was going to attempt to harm Queen Elizabeth and would do this either by dropping some object off the Golden Gate Bridge onto the royal yacht Britannia when it sails underneath, or would attempt to kill Queen Elizabeth when she visited Yosemite National Park,” it adds.

In response, the FBI had planned to “close the walkways on the Golden Gate Bridge as the yacht nears”. It is unclear what measures were taken at Yosemite, but the visit went ahead.

The file also refers to a San Francisco club which “has a popular reputation as a republican bar that is frequented by sympathisers with the Provisional Irish Republican Army (or IRA)”.

The cache of FBI files were made available after a Freedom of Information Act request submitted by US media outlets.

Another document relating to the Queen’s state visit to the US in 1991, reveals concerns that Irish groups were planning to protest at her attendance at a baseball game as well as a White House event.

The information came from the Philadelphia Irish paper titled Irish Edition.

“The article stated anti-British feelings are running high as a result of well publicised injustices inflicted on the Birmingham Six by the corrupt English judicial system and the recent rash of brutal murders of unarmed Irish nationalists in the six counties by loyalist death squads,” the file said.

A separate file among the documents, dated 1989, pointed out that while the FBI was unaware of any specific threats against the Queen “the possibility of threats against the British monarchy is ever present from the Irish Republican Army (IRA)”.