Nigel Farage has watered down his call for Britain to give asylum to Syrian refugees, suggesting the UK should only offer shelter to some Christians fleeing violence.

The Ukip leader appears to have modified his position after outrage from some within his own party, which has been campaigning against mass immigration from Romania and Bulgaria.

Over the weekend, Farage said there was a "responsibility on all of us in the free west to try and help some of those people in Syria fleeing in fear of their lives", challenging the government over its decision not to take any refugees from the war zone.

However, he shifted his stance on BBC Radio 2's Jeremy Vine Show on Monday, suggesting some Syrian Christians should be allowed to come to the UK but other countries should take Muslims.

"It's bad enough for Sunni and Shia, at least there are neighbouring countries that will take them," he said. "Where on earth are the Christians going to go? Christians are now a seriously persecuted minority … they are under assault from all sides."

In a statement on its website, Ukip said: "Christians are being increasingly persecuted across the Middle East and Syria as extreme Islamist elements seek to purge the region of Christianity. If we do not help these people then who will? We must as a nation help Christians who are fleeing Syria to escape death and torture by allowing some to come to the UK."

Farage made his call days after the government said it would focus its efforts on providing humanitarian help to Syrian refugees in the region rather than welcoming them to Britain.

Despite discontent among Ukip members, the remarks have already sparked a debate within the coalition about whether more could be done.

Earl Howe, a Tory health minister, said the government needed to look urgently at the issue of refugees and remember Britain's position as a country that looks after people in distress.

"There are people in desperate need, we cannot accommodate them all," he told BBC Radio 5 Live's Breakfast.

"I think the European Union has a duty to look at what it can do, both on the ground for those refugees from Syria but also whether we can accommodate some of them.

"I certainly think we should look at this and we have in the past been a country that looks kindly on people in distress and are the victims of violence in their native countries and that should not change."

However, Grant Shapps, the Conservative party chairman, insisted there has been no change in policy. He said letting in a few refugees would be "tokenistic" and insisted the best way of helping Syrians was financial aid.

Last week, David Cameron joined forces with Ed Miliband and Nick Clegg to endorse a £4bn UN appeal after a warning that nearly three-quarters of the Syrian population would need help in 2014. The three leaders said that the fate of a generation of Syrian children was hanging in the balance after figures show that 4 million young people were suffering as the conflict entered its third year.

But António Guterres, the United Nations high commissioner for refugees, told the Guardian this year that western countries such as Britain and the US may be asked to accept tens of thousands of refugees.

He said: "If things go on for a prolonged period of time, then resettlement will become a central part of our strategy. We would like when the time comes … to be able to launch a resettlement programme as massive as the one for Iraqis."