Claims that illegal British-made cluster bombs are being used by Saudi Arabia in the Yemen civil war is being investigated by the UK government.

The human rights charity Amnesty International said it had discovered evidence the Saudi-led coalition had used the banned bombs. Foreign secretary Philip Hammond told MPs the ministry of defence was "urgently investigating" the allegations.

He went on to say Britain had received assurances from the Saudis that the illegal bombs had not been used.

In reply to an urgent question in parliament on Tuesday, the defence minister Philip Dunne added the UK last delivered cluster bombs to Saudi Arabia in 1989 and no longer supplied, manufactured or supported them.

The retort comes after Amnesty wrote to the Prime Minister on Monday to call for a full investigation.

In 2008 the UK signed an international convention that banned the use of cluster bombs. Although neither Saudi Arabia or UAE, the other major state supporting the Saudi-led coalition, have signed the coalition, the bombs are designed to be dropped by a Tornado jet, dozens of which have been sold to Saudi Arabia from Britain in recent decades. The planes are still services by British mechanics, leading to the call for an investigation by Amnesty.

The bomb is designed to spread small pieces over a large area so its target is indiscriminate and a particular danger to civilians.

Amnesty International UK arms control director Oliver Sprague said: "Cluster bombs are one of the nastiest weapons in the history of warfare, rightly banned by more than 100 countries, so it's truly shocking that a British cluster munition has been dropped on a civilian area in Yemen.

"The UK should have been tracking down all the now-banned cluster bombs it's sold to Saudi Arabia over the years and pressing for them to be safely disposed of. Instead, shamefully, it's now come to light that a UK cluster bomb has been used in Yemen, spraying its deadly bomblets all over a village and jeopardising the lives of men, women and children.

"There needs to be a full investigation into both this incident and all aspects of the UK's arming of Saudi Arabia and other countries involved in the carnage in Yemen."