Britain in an "ideal world" should be aiming for zero net migration, according to Ukip's new leader.
But Henry Bolton said he was not suggesting this to be practical, noting it would be "very difficult" to hit such a target.
He added he did not want to provide an "arbitrary" figure as "nobody listening here will really believe" it can be hit.
Mr Bolton's desire for zero net migration echoes his party's 2017 general election commitment pushed by his predecessor Paul Nuttall.
In 2015, Ukip under Nigel Farage promised a temporary block on low-skilled and unskilled migration and a limit of 50,000 high-skilled immigrants a year.
Mr Bolton told Sky News' Sunday with Paterson: "We are as a country being swamped by the fact we're having a net immigration that is approximately the size of Wolverhampton or Hull ever year.
"That's difficult to cope with in terms of our services and infrastructure when we're cutting police by 25%, for example, local government in some cases by 50%. So you've got that problem."
Mr Bolton said the Government needs to "ramp up" policing and reverse local government cuts.
He rejected a request to provide a figure on how many people should be entering the UK, describing it as "arbitrary".
Pressed further, Mr Bolton said: "In an ideal world, and I'm not saying this is practical, we should be aiming - certainly for the next few years - to zero net immigration.
"But the chances of hitting zero net immigration, it's a very difficult target to hit - for no other reason than the fact net immigration is also affected by the number of people who leave the country, and we can't control how many people leave the country.
"So in terms of the overall number of people coming in, yeah, the ideal would be to bring it down to zero."
Mr Bolton added: "I'm not going to be going around saying that I'm going to be doing X, Y and Z and that Ukip is going to be doing X, Y and Z knowing that we can't.
"So in future when people hear something coming out of my mouth, when I say we're going to do this, it'll be because I sincerely believe we can achieve that.
"If I give you an arbitrary figure of 20,000 people net immigration then nobody listening here will really believe that we can hit a specific figure of 20,000.
"So you're going to hear from me what we can deliver."