Boris Johnson has faced demands for a more "humane" policy for refugees fleeing Ukraine as a top Tory urged him to reconsider the tone of the UK response.
The Prime Minister came under criticism from his own side as former Tory chief whip Julian Smith urged him to "look again" at the British visa process.
The UK has handed out fewer than 1,000 visas to Ukrainians fleeing the Russian invasion amid the largest refugee crisis in Europe since the Second World War.
Unlike many other European countries, Britain has insisted on maintaining security checks on people applying for sanctuary on its shores.
During a tense Prime Minister's Questions, Mr Johnson insisted checks were needed because the Kremlin had singled out Britain over its stance on the crisis in Ukraine.
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He claimed "no one has been turned away" despite reports of chaos at Calais, where arrivals have been told to travel to Paris or Brussels to get their visas.
No10 said the pop-up centre in Lille will start taking appointments from tomorrow.
Ex-Cabinet Minister Julian Smith said: "People across the country are genuinely concerned on our response on refugees, on the bureaucracy, on the tone of our response.
"He's shown with vaccines that Government change really comes from the very top.
"Please can I urge him to look again on resetting our policy and taking control of a more humane approach to those women and men fleeing from Ukraine.
Mr Johnson replied: "We have done more than any other to resettle vulnerable people since 2015.
"I think there is a huge opportunity for us to do more which is why the Secretary of State for Levelling Up [Michael Gove] will be setting out a route by which the British people... can offer a home to people fleeing Ukraine."
He said Mr Gove would be setting out more details on the sponsorship route in the next few days.
Downing Street confirmed the Prime Minister was referring to the humanitarian sponsorship route which has already been announced, but not launched.
No10 said more details on the sponsorship route will be announced by the end of this week.
The PM’s deputy spokesman said details was not yet confirmed, but “we will look at all options” - including for people to “open up their homes” to Ukrainians.
No10 added that when the PM said it could benefit hundreds of thousands of people, he was referring to the fact there is no cap on the scheme.
Some 957 Ukraine family visas have now been given out so far, No10 said.
SNP Westminster leader Ian Blackford blasted the Government for failing to understand the urgency of the problem.
He said: "These are people fleeing war crimes, torn apart from their families as their homes are shelled. And the Home Secretary is blocking them with endless paperwork.
"This isn't just incompetence, this is ideology."
He accused the Government of refusing to set aside its hostile environment policy in the face of Europe's largest post-war refugee crisis.
"The UK Home Office is raising barriers and bureaucracy when we should be offering care and compassion. Prime Minister, do not let the history of failure repeat itself."
But the PM hit back, saying the UK had "an unparalleled record" to helping refugees.
"He lectures the Home Secretary - this is a Government unlike any other, the Prime Minister, the Deputy Prime Minister, the Home Secretary, are directly descended from refugees," he said.
"We understand how much refugees have to give to this country and we understand what this country has to gain from welcoming refugees and we will be generous and we are being generous, and what we are doing is making sure that in those neighbouring countries the UK is out in front giving the humanitarian assistance."
