The new scheme will see up to 20,000 Afghans offered a route to set up home in the UK in the coming years.
In the first year, 5,000 refugees will be eligible – with women, girls and others in need having priority.
Home Secretary Priti Patel urged other countries to help, writing in the Daily Telegraph “we cannot do this alone”.
However, opposition parties have criticised the settlement scheme for not going far enough.
The new plan is on top of the existing scheme for interpreters and other staff who worked for the UK.
Some 5,000 Afghans and family members are expected to benefit from that policy.
Parliament has been recalled and Prime Minister Boris Johnson is to open a debate in the House of Commons about the situation in Afghanistan from 09:30 BST on Wednesday.
Downing Street said Mr Johnson spoke to US President Joe Biden on Tuesday evening about the evacuation of Kabul.
The leaders “resolved to continue working closely together on this in the days and weeks ahead to allow as many people as possible to leave the country”, a spokesperson said.
“The prime minister stressed the importance of not losing the gains made in Afghanistan over the last 20 years, of protecting ourselves against any emerging threat from terrorism, and of continuing to support the people of Afghanistan.”
Announcing the new Afghan Citizens’ Resettlement Scheme, Mr Johnson said: “We owe a debt of gratitude to all those who have worked with us to make Afghanistan a better place over the last twenty years.
“Many of them, particularly women, are now in urgent need of our help. I am proud that the UK has been able to put in place this route to help them and their families live safely in the UK.”
Ms Patel wrote in the Telegraph that she wanted to ensure the UK was doing “everything possible to provide support to the most vulnerable fleeing Afghanistan so they can start a new life in safety in the UK”.
She added: “The UK is also doing all it can to encourage other countries to help. Not only do we want to lead by example, we cannot do this alone.”
The government emphasised the new scheme would “not compromise on national security” and has promised all those arriving will have to pass “strict security checks”.
Among those to criticise the scheme was Tory MP Tobias Ellwood, chairman of the Defence Select Committee, who told the Daily Mirror it was a “woefully inadequate response”, citing the government capping numbers at 5,000 for the first year when “the threat is at its greatest”.
Shadow home secretary Nick Thomas-Symonds welcomed the government putting a scheme in place but said there needed to be a “more urgent plan of action”.
“This proposal does not meet the scale of the challenge,” he added.
The Lib Dems foreign affairs spokeswoman Layla Moran said that “20,000 should be the starting point of this scheme, not the target”.
And Ian Blackford, the SNP’s leader in Westminster, tweeted that the scheme didn’t “go anywhere near far or fast enough” and the target should be at least 35,000 to 40,000 Afghan refugees. (Courtesy BBC)