Government analysis has reportedly indicated British-made cluster bombs have been used by Saudi Arabia-led forces in the war in Yemen.
Defence Secretary Michael Fallon is among ministers to have been made aware of the analysis, sources told the Guardian.
He is due to make a statement to MPs on arms exports on Monday afternoon.
Amnesty International has called for an immediate suspension of all arms sales to Saudi Arabia "that risk fuelling these appalling atrocities in Yemen".
In October, ITV News were shown photographs provided by a Houthi fighter that suggested British cluster bombs have been used in the war.
The fighter said they were taken last March in the front line region of Baqim and metadata on the photographs supported his account.
An independent munitions expert also identified the bombs as British-made IBL755s.
Cluster bombs were prohibited in 2010 in an international treaty signed by Britain, because of the risk to civilians.
The government declined to comment on the latest claims but said it takes the allegations "very seriously" and has raised them with the Saudi-led coalition.
The prime minister of Yemen's rebel Houthi government accused the UK of "war crimes" for supplying the banned weapons.
Abdel-Aziz bin Habtour said: "They have sold cluster bombs to Saudi Arabia.
"They know the Saudis are going to drop them on Yemen ... in Sa'adah and in Sana'a and other provinces.
"I don't think they are guilty of war crimes, I believe so. They are participating in the bombing of Yemen people."
A government spokesman said: "We have analysed the case carefully using all available information, considering all possibilities, and raised the issue with the Saudi-led coalition."
Amnesty International said the "belated 'investigation' within the Ministry of Defence" should lead to a suspension of arms sales to Saudi Arabia.