Priti Patel ruled out a visa waiver for Ukrainians fleeing the conflict with Russia because of fears that Moscow’s troops and extremists could seek to come to the UK.

The Home Secretary, who has come under intense political pressure from MPs across the Commons to do more to allow Ukrainian refugees to reach the UK, insisted she was taking action to open safe routes.

She told MPs she was following the “strongest security advice” as she rejected the call to scrap the need for visas.

“Over the weekend I have seen members of this House calling for full visa waivers for all Ukrainians,” Ms Patel said.

“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.”

The Home Secretary said the first phase of the “bespoke humanitarian route” being created for Ukrainians to enter the UK would allow around 100,000 people to come to “seek sanctuary”.

The 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.

“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,” Ms Patel said.

“Giving British nationals and any person settled in the UK the ability to bring over their immediate Ukrainian family members.”

The Home Secretary also set out plans to tighten the Nationality and Borders Bill, which is currently going through Parliament.

The moves could make it harder for Russians to obtain visas to enter the UK.

The legislation allows Ms Patel to suspend visas entirely, impose a £190 surcharge on applications to come to the UK or increase visa processing times.

Currently that power is limited to countries that refuse to co-operate with the return of their nationals but Ms Patel said the powers would be extended to cover countries that have “taken significant steps which threaten international peace and security”.

Ms Patel’s comments in the Commons came after senior Tory MPs urged Boris Johnson to do more to take in Ukrainians.

Former Cabinet ministers Sir Robert Buckland, Jeremy Hunt, Damian Green and Matt Hancock were among the MPs to put their names to the letter calling for a “flexible and pragmatic approach” to allow Ukrainians to seek temporary refuge in the UK.

The 38 Tory MPs said: “It is clear that this is not another migration crisis; this is a crisis of war. 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.”

Opposition figures criticised Ms Patel’s “chaotic” response to the crisis.

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.”