A senior United Nations official has called on Britain to take more people fleeing Syria after shocking pictures of a drowned refugee boy ratcheted up the pressure on Europe's leaders to act.

Peter Sutherland, the UN special representative on international migration, said while some countries were "massively bearing the burden" of the migrant crisis, the UK was among those that "can do more".

A Government spokesman said pictures of the three-year-old child washed up on a Turkish beach were "clearly shocking".

However, after David Cameron said simply taking more migrants was not the answer to the crisis, the spokesman emphasised that the UK was at the forefront of international efforts to help refugees in the region.

Pressure was continuing to build on Mr Cameron as Labour leadership contender Andy Burnham called for Parliament to debate whether the UK should take in more refugees.

Meanwhile figures show the number of migrant children who have been smuggled across the Channel and taken into care in Britain has risen since to 720.

The numbers have risen by almost 100 in the space of a month, when Kent County Council said it had no more foster beds available, BBC Radio Kent reported.

There has been a dramatic rise in the number of young migrants in the local authority's care amid this summer's turmoil in Calais, leaving it with a multi-million pound funding gap in care costs.

Mr Burnham urged Mr Cameron to call a debate and vote on the refugee crisis when Parliament returns next week.

"Over this summer, we have seen an unfolding humanitarian crisis of epic proportions across the Mediterranean and mainland Europe," he said.

"But the response of David Cameron and his ministers has veered from the inadequate to the misjudged.

"His Government's inaction as the situation has escalated is a stain on our nation's conscience.

"If the Prime Minister refused to act, then my first act as leader would be to apply to the Speaker for an emergency debate on the refugee crisis."

His comments came after his Labour leadership rival Yvette Cooper, suggested the UK could take 10,000 Syrian refugees.

Lib Dem leader Tim Farron said the Government's refusal to take more than a few hundred refugees was "morally wrong" and "politically foolish" while Scotland's First Minister Nicola Sturgeon said: "We must do more".

Speaking on BBC2's Newsnight, Mr SutherIand said that the crisis demanded a united response from Europe's leaders and that Britain needed to play its part.

"I think that this country can do more. The only way to solve this problem is by a united European response and that means sharing responsibility for appalling suffering," he said.

"This is a humanitarian crisis that Europe has not experienced in our time of a dimension which demands a common response.

"At the moment it is true to say that a number of countries are massively bearing the burden of this."

While Mr Sutherland said Germany, Sweden, France and Italy were among those doing their bit, the Government spokesman insisted the UK was also playing its part.

"These photos are clearly shocking. This is why we continue to be at the forefront of the international response to the humanitarian crisis in Syria - including as the second biggest bilateral donor of humanitarian aid, having already pledged £900 million," the spokesman said.

"In addition to this financial support, we have granted protection to almost 5,000 Syrians since the crisis began and continue to tackle the organised trafficking gangs seeking to profit from this human misery."

The boy - seen lying face down on the shore - was reported to be one of a group of at least 12 people who drowned when their flimsy boats collapsed as they headed for the Greek island of Kos.

He was named in Turkish media reports as Aylan Kurdi who fled last year with his family from the besieged town of Kobane to escape the advance of Islamic State militants.

His five-year-old brother, Galip, and their mother, Rhian, were also reported to be among the dead. Their father, Abdullah Kurdi, was said to have survived.

They were reported to be among a group of 23 people who set off in two boats from the Bodrum peninsula in Turkey early on Wednesday in an attempt to make the hazardous crossing to Greek territory.

Only nine are thought to have survived, while two are believed to be still missing.

Justin Forsyth, chief executive of Save the Children, said: "This tragic image of a little boy who's lost his life fleeing Syria is shocking and is a reminder of the dangers children and families are taking in search of a better life.

"This child's plight should concentrate minds and force the EU to come together and agree to a plan to tackle the refugee crisis."

A number of Conservative MPs have spoken out to say Britain should do more for Syrian refugees.

Nadhim Zahawi said those fleeing the war-torn country had been "failed".

The MP for Stratford-on-Avon is an Iraqi immigrant who came to the UK with his family aged nine after fleeing Saddam Hussein's regime.

He wrote on Twitter: "We r nothing without compassion. Pic should make us all ashamed. We have failed in Syria. I am sorry little angel, RIP."

Tom Tugendhat, MP for Tonbridge, Edenbridge and Malling said: "Our common humanity demands action at home and abroad."

David Burrowes, MP for Enfield Southgate, tweeted: " ... at the very least we should accept more than 1% Syrian refugees because we accept more than 1% responsibility..."