Priti Patel has signalled a new Conservative government would abandon setting any specific targets on limiting immigration.
The home secretary told ITV News that "arbitrary targets undermine public confidence" and declined to commit to them in the future.
Theresa May's government had made a pledge to reduce immigration to "tens of thousands" but that goal - and indeed any such target - appears now to be scrapped.
Ms Patel was asked by ITV News whether she had "learned not to set any targets", to which she replied: "Well, I think that by taking back control and effectively having a points-based system specifically, we can give the public confidence in the immigration system...
"And speaking about targets, targets are an arbitrary figure, and clearly that is where public confidence has been eroded in the past.
"Rather than talk about arbitrary numbers, and targets that undermine public confidence when they're not met and haven't been met in the past."
Boris Johnson later said the Conservative Party's immigration plans "may mean in some sectors immigration comes down".
The Prime Minister said he is in favour of "people of talent" moving to the UK before telling broadcasters: "Let's be frank, over the last 20, 30 years - 20 years in particular - we've seen a lot of people coming without the job to go to, they have been putting pressure on public services and they haven't necessarily had the skills the economy demands.
"We want to have a controlled system."
The Prime Minister said he expected this to help businesses attract the people they want, adding: "And yes, that may mean in some sectors immigration comes down.
"Frankly, that's great because I think there's been a lot of pressure on the system."
But the PM also reiterated: "I do not want a country that is going to be closed to the wider world."
Ms Patel also took aim at Labour's "open borders" policy, saying immigration would "surge" if Jeremy Corbyn became prime minister.
She said if Diane Abbott were to become home secretary, Labour would "extend free movement" to the rest of the world, meaning that up to 800,000 more people could come into the UK every year.
But Labour said the Conservatives' claim was the latest from the Tories “make-believe research department”.
Security Minister Brandon Lewis had earlier told BBC Radio 4's Today programme: "We are not setting some arbitrary target.
"We want to introduce a new points-based system that is fair and equal to the entire world. That gives us control and we can then see immigration being reduced."
The Conservatives they have laid out plans for an Australian "points-based" system, based on skills and other factors, to determine whether EU or non-EU migrants can come to the UK.
According to research by the Conservatives, extending free movement to the rest of the world would result in average net immigration to the UK of 840,000 a year over the next 10 years.
“This is equivalent to the combined populations of Manchester and Newcastle moving to the UK every single year,” the Tories said.
“This means that levels of net migration would more than treble if Labour introduced their proposals for completely open borders.”
The Tories added the analysis is “deliberately cautious and is likely to provide a significant underestimate of net inflows from non-EEA countries under Labour’s plans”.
The party also said maintaining free movement with existing EEA members would result in average net immigration to the UK of 260,000 a year over the next decade.
Labour has yet to outline its own policy, but shadow business minister Laura Pidcock said she would not be drawn into setting an "arbitrary figure".
Meanwhile Diane Abbott, Labour’s shadow home secretary, said: “This is more fake news from the Conservative Party’s make-believe research department.
“Unlike the Tories, we won’t scapegoat migrants or deport our own Windrush-generation citizens.
“The damage done to our society has been through damaging Conservative cuts to our public services, not by EU nationals coming to work in them.”
Speaking on Radio 4's Today Programme, Ms Pidcock said: "What we are certainly not going to do is put the lives of people on the line here in a General Election campaign."
Ms Pidcock said: "I think it's a false flag, this issue of immigration."
She added: "We know actually that migrant labour does not undercut wages, it is exploitative bosses that seek to undermine national agreements - that's our emphasis."
Questioned on whether she would be happy for immigration to rise under a Labour government, Ms Pidcock added: "I think these targets are arbitrary."
Although Labour has yet to release its immigration policy, Unite leader Len McCluskey told the Guardian it would not be "sensible" to extend the freedom of movement policy.
At Labour's conference in September, Labour party members voted in favour of increasing freedom of movement.
Ms Pidcock said of Mr McCluskey's remarks: "He is the leader of the trade union that I am a member of, he talked very clearly about there not being an environment where national terms and conditions can be undermined by exploitative bosses."