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The splintered fluorine atoms, the researchers report, are safely sequestered by reacting them with potassium hydride in solution to form potassium fluoride, a nontoxic ingredient in toothpaste.

In 2013, a team of researchers led by Sanford showed9 how to make such bonds with a safer potassium fluoride salt using a copper catalyst.

It said the award by the previous Labour government of five licences for the export of sodium fluoride had been "highly questionable", while the decision of the current government to issue a further two licences for sodium and potassium fluoride after the civil war had begun was irresponsible.

In correspondence with the committee, Mr Cable had said the licences for the export of sodium fluoride and potassium fluoride were granted after an assessment in relation to both EU and UK rules - including whether there was a "clear risk that they might be used for internal repression" - and concluded there were no grounds for refusal.

The government has rejected newspaper claims, made over the weekend, that the UK exported potassium fluoride and sodium fluoride, which could have been used to make nerve agents.