Home Secretary Priti Patel has said 100,000 Ukrainians will be able to seek refuge in the UK under a "humanitarian route".
However, she was met with fury after refusing to waive tough visa rules for security reasons, citing concerns extremists could take advantages of the change.
Ms Patel confirmed to MPs that family members of British nationals would be allowed to come to the UK for up to a year providing they pass security checks, the Mirror reported.
This change will apply to "immediate" family members.
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But she later rejected calls to waive tough visa rules for security reasons because of fears that Moscow’s troops and extremists could seek to come to the UK.
It comes as the Government has faced mounting pressure allow more Ukrainian refugees to seek sanctuary in the UK.
Speaking in the Commons, Ms Patel: "Through this extension alone I can confirm that an additional 100,000 Ukrainians will be able to seek sanctuary in the UK, with access to work and public services.
"We are enabling Ukrainian nationals already in the UK, giving them the ability to switch free of charge into a points-based immigration route or through the family visa route.
"We are extending visas for (Ukraine) temporary workers in some sectors and they can now stay until at least December 2022."
She rejected calls for full visa waivers for Ukrainians - and said security checks remained a fundamental part of the process.
"That is vital to keep British citizens safe and to ensure that we are helping those in genuine need, particularly as Russian troops are now infiltrating Ukraine and merging into Ukrainian forces," she said.
"Intelligence reports also state the presence of extremist groups and organisations who threaten the region but also our domestic homeland.
"We know all too well what Putin's Russia is willing to do, even on our soil, as we saw through the Salisbury attack."
But Shadow Home Secretary Yvette Cooper said it was "extremely unclear" how the scheme would actually work - and blasted Ms Patel for being "poorly prepared" for the crisis.
"Why is there is so much confusion about this? The Russian invasion began five days ago," she said.
"Why is nothing worked out already and how on earth is the Home Secretary so poorly prepared for something she has been warned about for so many weeks?"
The row comes as a string of senior Tories ramped up pressure on Boris Johnson to offer refuge to Ukrainian people.
“It is clear that this is not another migration crisis; this is a crisis of war," says the letter from 37 members of the One Nation Tory group, seen by The Guardian.
"This should not be business as usual, we need sincere and immediate support for the Ukrainian people.
"The United Kingdom cannot flag or fail, our message must be clear: Ukrainian victims of war seeking refuge are welcome."
The Prime Minister's spokesman said: "The PM is committed to being as generous as he possible can as we have been with refugees in other areas like Syria.
"We have a strong record in providing full support on visas. We want to work with the Ukrainian government on what they most need support with."
Rosie Carter, Director of Policy at HOPE not hate, added: "The war in Ukraine has exposed the government’s attempts to play immigration as a political football as cynical and inhumane in the face of a crisis where leaders across the world are standing together to support refugees.
“It is crucial that the UK creates safe and legal routes for people fleeing war and persecution, rather than squeezing people who are forced to flee war through an increasingly restrictive and cruel asylum system."
