Priti Patel has rejected calls for a full visa waiver for Ukrainians fleeing the conflict with Russia.
The home secretary had been urged to provide a sanctuary route for all those who need it.
But Patel cited security concerns in her decision to reject a full waiver for all Ukrainians.
Speaking in the House of Commons on Monday, Patel told MPs that she was following the “strongest security advice” regarding whether to scrap visas.
But, the Cabinet secretary said that the first phase of a “bespoke humanitarian route” being created would allow 100,000 Ukrainians to come to the UK to “seek sanctuary”.
The UK Government has already announced measures allowing people who are settled in the UK to be able to bring their Ukrainian immediate family members to join them.
“Over the weekend I have seen members of this House calling for full visa waivers for all Ukrainians,” said Patel.
“Security and biometric checks are a fundamental part of our visa approval process worldwide and will continue, as they did for the evacuation of people from Afghanistan.
“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.
“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.”
Patel continued: “Where family members of British nationals do not meet the usual eligibility criteria, but pass security checks, UK visas and immigration will give them the permission to enter the UK outside the rules for 12 months and is prioritising all applications.
“Giving British nationals and any person settled in the UK the ability to bring over their immediate Ukrainian family members.”
Opposition figures criticised Patel’s “chaotic” response to the crisis.
Labour’s shadow home secretary Yvette Cooper said: “The home secretary has just said she is announcing a bespoke humanitarian route but it’s extremely unclear from what she’s said what the details actually are or who it will apply to.”
Liberal Democrat home affairs spokesman Alistair Carmichael said: “Ukrainians are fleeing for their lives.
“They deserve far better than just more spin and confusion from our Government.
“The home secretary should come back to Parliament urgently to announce a full refugee scheme to resettle Ukrainians in the UK.”
Meanwhile, the Foreign Office has advised Britons against all travel to Russia because of the “lack of available flight options to return to the UK, and the increased volatility in the Russian economy”.