Ministers have been sharply criticised by MPs for relying on Saudi Arabia to investigate allegations of human rights violations by its forces in Yemen amid claims UK-made weapons are fuelling the country's bloody civil war.
The Commons International Development Committee said it was "unconvinced" the Saudis were best placed to inquire into alleged breaches of international humanitarian law (IHL) by the coalition it is leading in support of the Yemeni government.
It said the growing evidence of "indiscriminate bombing" by the coalition forces fighting the Iranian-backed Houthi rebels, raised "serious questions" over the Government's continued licensing of arms sales to the Saudis.
In a letter to the committee, Foreign Secretary Philip Hammond said the Saudis had recently appointed a new investigation team outside of the coalition command structure to look at the issue of IHL violations.
"We believe we should give time for this new team to do its job before considering the issue of an independent investigation," he wrote.
In its report, however, the committee said it was a long-standing principle of the rule of law that such inquiries should be independent of those being investigated.
"We are concerned that any investigation led by coalition actors is likely to come to the conclusion that the allegations were inaccurate," it said.
"The growing evidence of indiscriminate bombing by the Saudi-led coalition in Yemen, in violation of IHL, raises serious questions over the Government's continued licensing of arms transfers to Saudi Arabia.
"If there is a risk that it contravenes the UK's obligations under the laws which regulate the international arms trade, the UK should not be providing arms to one of the parties to the conflict."
A Government spokeswoman said that they encouraged all sides to the conflict in Yemen to conduct "thorough and conclusive investigations" into all alleged breaches of international humanitarian law.
"Following the standards we set ourselves and our allies, we believe it is most effective for the Saudi Arabian authorities to carry out investigations where they are alleged to have breached IHL," the spokeswoman said.
"We encourage them to continue and complete this process in good time."