British Prime Minister David Cameron came under pressure on Thursday to take in more refugees after the image of a dead Syrian toddler washed up on a Turkish beach raised the emotional temperature of the debate.

Cameron was widely criticised for saying on Wednesday that he did not think the answer was to take more and more refugees but to bring peace and stability to the Middle East, hours before the harrowing image emerged.

"Mr Cameron, summer is over ... Now deal with the biggest crisis facing Europe since WW2," read a headline on the front page of the Sun, Britain's highest-selling newspaper, above the image of the lifeless boy being carried away.

The change of tone from a newspaper criticised by the United Nations rights chief in April after one of its columnists compared migrants to "cockroaches", was a mark of the emotional impact of the images of human suffering across Europe.

"We r nothing without compassion. Pic should make us all ashamed. We have failed in Syria. I am sorry little angel, RIP," wrote Nadhim Zahawi, a member of parliament from Cameron's Conservative Party, on Twitter, above a picture of the Syrian boy.

Some other Conservative legislators also spoke out in favour of a more compassionate stance. Tom Tugendhat tweeted that many of his constituents wanted Britain to do more and he agreed with them, while the BBC quoted Johnny Mercer as saying mothers trying to keep their children afloat on life jackets should not think of the UK as a place that did not welcome them.

Since the start of the Syrian war, Britain has taken in 216 people under a U.N.-backed relocation scheme for vulnerable Syrians, and about 5,000 Syrian refugees who were able to reach Britain by their own means.

The government says that while Britain has taken in fewer refugees than other European countries, it is the most generous donor of aid money to humanitarian organisations helping Syrians in their own country and in refugee camps in the Middle East.

But a growing chorus of critics has dismissed that response as inadequate in the face of the unfolding tragedy.

Yvette Cooper, one of four candidates to lead the opposition Labour Party, said in a speech Britain should take in an additional 10,000 refugees.

David Miliband, a former Labour foreign secretary who now runs the International Rescue Committee, a non-governmental organisation, said he refused to believe that Britain had reached the limit of its capacity to take in refugees.

In a sign of growing grassroots disquiet with the official stance, a plan to stage a march next week through central London to Cameron's Downing Street office to show solidarity with refugees was gaining traction on Facebook.

A petition on parliament's website to accept more refugees and increase support for them had garnered close to 100,000 signatures.