“For example, action could be brought against the UK government by victims of Jihadi John for our failure to prevent him from travelling to Syria.

“The Act consequently encourages the use of ambulance chasing lawyers in America due to the large and diverse number of suits that can be brought against foreign governments.”

What began as a “noble endeavour to ensure victims of terror” can get justice has become a “threat to national sovereignty” that weakens international efforts to fight terrorism.

The letter continues: “The EU has warned that Jasta raises the “inherent danger of causing reciprocal action” from the legislatures of other nations. This puts at risk not only the US, but the UK as well as it opens up a Pandora’s Box of potential lawsuits that can come from anywhere.”

The passing of the law has plunged US relations with Saudi Arabia into crisis. The kingdom lobbied hard against it, only for US lawmakers in both houses to show overwhelming support for the new law.

Saudi Arabia warned it could begin pulling its vast investments from the United States if it felt they were in danger of being seized as part of legal proceedings.