When somebody tells you, "If we had wanted war we would have stayed in Syria," it really makes you think.

I've done a lot of thinking since returning from Serbia a few weeks ago.

Until March this year, thousands of refugees were crossing into Serbia every day on long, often treacherous journeys towards sanctuary, in search of safer lives than those they had left behind.

Over time, countries throughout the West Balkans effectively closed their borders. The implementation of a deal struck in March between the European Union and Turkey has more or less stopped the flow of refugees crossing the Aegean Sea into Greece and north into the rest of Europe.

In Greece, some 50,000 refugees are stranded. They find themselves unable to travel onwards and, understandably, determined not to go back to countries ravaged by conflict. Much has been written about the plight of refugees in Greece, but far less about those who now find themselves stranded in Serbia.

The scene at the reception centre in Presevo on the Serbia-Macedonia border was not what I was expecting. At that time, just 66 refugees were staying at the centre. Rows of immaculate bunk beds ready to accommodate those arriving lay empty. Our ACT Alliance partner, Philanthropy, part of the Serbian Orthodox Church, continues to respond to an ever-changing situation, providing essential practical support such as sleeping bags, food and toiletries.

The challenge for them is the unpredictability of the need for their help. At any time the number of arrivals could change and they could, with little warning, find themselves coping with a huge increase in arrivals of desperate, exhausted people.

Just last week we learnt that arrivals in Serbia are once again increasing, to 500 people per day. At their wits' end, with borders still mostly shut and with no political solution in sight, refugees are increasingly turning to traffickers to help them cross borders illegally. Staff at Philanthropy tell us that the people they now see arriving are in a poor physical state, exhausted by treacherous and physically demanding journeys, often in need of medical assistance. Many are children.

Hearing this news back in London, I'm once again reminded of those words spoken to me by a young Syrian man. He talked about how unwelcome and unwanted he feels in Europe. He sensed a level of hostility towards him, and his fellow refugees, which he couldn't understand. He had crossed the Aegean Sea overnight to reach Greece. But having arrived, he has found no welcome. His words spoke of his bewilderment at feeling unwanted, and they made me feel deeply ashamed.

How can we in Europe defend that perceived hostility towards people who have been forced to leave behind everything of their lives?

I've since tried to imagine how bad things must be to get into an overcrowded, possibly unseaworthy, boat. To head out into the pitch blackness of the night, towards an uncertain future, knowing that many hundreds of people who have gone before you have died while attempting to make the same journey.

How can we, in Europe and specifically in the UK, look away and say that we do not want people like that young Syrian, and so very many others?

The UK is the world's fifth biggest economy; the EU has more than 500 million citizens. It is not beyond our ability to accept and positively welcome fellow human beings who have been forced to leave behind the very things that matter so much to us – homes, families, friends, jobs, security, and identity.

The problem is political will, or rather our lack of it. In the UK, as in so many other European countries, we could do much more than we are, but our politicians insist and even rely on seeing refugees as a problem to be kept at a distance – not on our shores. The lack of compassion is staggering.

The UK, with other European countries, has a responsibility to take a fair and proportionate number of refugees, including those who have already reached Europe. We should be providing safe and legal means for refugees to get this far, because there but for the grace of God go any of us.

Jenny Brown works for Christian Aid, which is currently operating in Greece and Serbia through ACT Alliance. Its partners are providing essential humanitarian support, as well as legal protection services to unaccompanied children in Greece. Christian Aid is calling on the UK government to take a fair and proportionate share of refugees and to provide safe and legal routes for refugees to travel to and through Europe.