Net migration should be capped at 50,000 a year, says Nigel Farage.
The Brexit Party leader told a BBC Question Time Leaders Special that the figure should return to a "sensible post-war number".
Net migration is the difference between the number of people who arrive in a country and those who leave - and in the year ending March 2019, the figure for the UK was 226,000.
Mr Farage also rejected claims his party were racist.
The special BBC One programme - part of a series with party leaders ahead of the general election - will air at 22:45 GMT.
Mr Farage first mentioned the 50,000 figure when he was leader of UKIP.
In its 2015 manifesto, the party said it would "limit highly-skilled work visas to 50,000 per annum, including those from the EU, and apply a moratorium to unskilled and low-skilled labour over the course of the next Parliament".
Asked by the BBC's Fiona Bruce whether his new party stood by the pledge, he told audience members in Peterborough: "I do not think that our quality of life in this country improves as our population heads inexorably towards 70 million, which is where it's going to be by the end of the 2020s.
"For 60 years after World War Two, we had annual net migration running at 30,000 to 50,000 a year. We had, actually, of all the European countries, the most successful integration. Things worked here well.
"For the last 10 years, it's been running at between a quarter of a million and a third of a million every year. We need to bring settlement down to that kind of sensible post-war number."
Mr Farage said he would allow for a "work permit system" to let people come to fill jobs - such as vacancies in the NHS.
But he added: "Because you come here to get a job, just as if you went to 200 countries and got a job, it doesn't give you the automatic right to settle and doesn't give you the automatic right to citizenship."
The Conservatives had promised to bring immigration below 100,000 each year - but it is widely expected for the pledge to be dropped by Boris Johnson.
However, the PM has said he will seek to reduce unskilled migration coming into the UK if the Tories win the election, and will introduce a points-based system for immigration.
Labour's Jeremy Corbyn has ruled out an "arbitrary figure" saying people should be "realistic" about needing immigration to fill jobs so the economy's needs can be met.
'Nobody else dared'
Mr Farage was then asked by the audience for his response to claims he was racist.
The Brexit Party leader said the accusation had been levelled at him in the past, adding: "You know why? Because nobody else dared talk about [immigration].
"The issue had been brushed under the carpet, despite the fact at the time it was the number one issue in British politics."
After calling for illegal immigration to be a debated topic during the campaign, an audience member then said the Brexit Party had been accused of being racist.
"No, it's not," said Mr Farage. "We had more ethnic diversity in our candidates for the European elections than the other parties added up together, so I won't have that."
He also defended the use of the controversial "breaking point" anti-EU poster he used in the 2016 referendum that showed a long queue of migrants waiting to cross the border into Slovenia.
Mr Farage said most of the people in the poster were economic migrants, men aged between 18 and 30, rather than refugees.
When will we hear from the other leaders?
BBC One will show another leader's special with co-leader of the Green Party Jonathan Bartley on Wednesday at 22:45.
Then on Friday at 19:00, Boris Johnson, Jeremy Corbyn, Nicola Sturgeon and Jo Swinson will all take part in a live Question Time Leaders Special from Sheffield.