The international aid agency Oxfam criticised Britain's policy of selling arms to Saudi Arabia, and described ministers as being in "denial and disarray".
Oxfam accused Britain of going from being an "enthusiastic backer" of the Arms Trade Treaty to "one of the most significant violators" and is expected to raise the issue of sales to Saudi Arabia at the second conference of states party to the treaty in Geneva today.
Penny Lawrence, deputy chief executive of Oxfam GB, will tell the conference that British weapons are fuelling a "brutal war in Yemen, harming the very people the Arms Trade Treaty is designed to protect," reports the BBC. "Schools, hospitals and homes have been bombed in contravention of the rules of war."
"The UK government is in denial and disarray over its arms sales to the Saudi-led coalition bombing campaign in Yemen," she will add.
"It has misled its own parliament about its oversight of arms sales and its international credibility is in jeopardy as it commits to action on paper but does the opposite in reality."
A British government spokesperson responded by saying the UK took the matter "very seriously" and it is "satisfied that extant licences for Saudi Arabia are compliant with the UK's export licensing criteria".
"The key test for our continued arms exports to Saudi Arabia in relation to international humanitarian law (IHL) is whether there is a clear risk that those weapons might be used in a serious violation of IHL," the spokesperson added.
"The situation is kept under careful and continual review."