David Cameron is under pressure to recall Parliament to discuss the plight of minorities fleeing the advance of Islamic State fighters in Iraq.
The prime minister is understood to be reluctant to bolster US air and drone strikes upon IS artillery positions with UK warplanes, especially after losing a vote on military intervention in Syria last year.
But it is likely that Britain will step up humanitarian efforts in the country, with Downing Street describing the situation as "deeply worrying".
An RAF airdrop on Saturday delivered water, ready-to-eat meals and solar lanterns to the tens of thousands of members of the Yazidi minority effectively trapped on the mountains of Sinjar, with a total aid package of £8million already announced.
In addition, the number of UK advisers in Erbil, the capital of the Kurdistan Regional Government in Iraq, will be increased.
The peshmerga troops of Kurdistan, an autonomous region of Iraq, have so far provided the only consistent defence against the advance of jihadists, but, while well-disciplined, they are poorly armed compared to the battle-hardened Islamists, who have looted state-of-the-art weaponry from the Iraqi army.
Tory MP Conor Burns urged the prime minister to recall MPs.
"These are our brothers who are being slaughtered, beheaded, raped and buried alive at the hands of Islamo-fascists who do not seek to take territory but are waging a cultural war. They despise our values, our liberalism and our Christianity. Whilst I welcome the aid, I don’t think it is a good enough response," he said.
"We in part created this mess, Parliament should come back to discuss what Britain can do."
David Cameron, meanwhile, is on holiday in Portugal.
While he has presumably stopped pointing at fish and politicians are entitled to holidays - and very able to be kept informed and make decisions - it does still seem incongruous that while the West reacts to prevent a potential genocide (and we use that word very carefully) in Iraq, the prime minister is out of the country on a family holiday.
Even more incongruous was Barack Obama's decision to go ahead with a two-week planned vacation in Martha's Vineyard just as he confirmed he would be the fourth US president in a row to bomb Iraq.
These photos were all taken this weekend: