The United Kingdom will resume weapons sales to Saudi Arabia despite international concerns that some could be used in the war in Yemen.

International Trade Secretary Liz Truss told Parliament on Tuesday that a government assessment suggested, "There is not a clear risk that the export of arms and military equipment to Saudi Arabia might be used in the commission of a serious violation of [international humanitarian law]".

Opposition legislators and campaigners against the arms trade slammed the "morally indefensible" decision by Prime Minister Boris Johnson's Conservative government.

The move followed a court ruling last year that the UK's licensing of arms sales to Saudi Arabia was unlawful, after campaigners argued the government had failed to make a proper assessment of humanitarian risks.

While the court's decision did not mean the UK had to halt arms exports to Saudi Arabia, it did mean it had to pause the granting of new export licences to sell arms to the kingdom - the UK's biggest weapons purchaser.

Truss said the government had "now re-taken the decisions that were the subject of judicial review on the correct legal basis, as required".

"It follows that the undertaking [given] to the court -that we would not grant any new licences for the export of arms or military equipment to Saudi Arabia for possible use in Yemen - falls away," she said in a written statement.

-Agencies