David Coburn said that having more children was the key to the country's population problems, not greater numbers of migrants.
Mr Coburn pulled off a surprise win in the European elections with 10.4% of the vote to become his party's first elected parliamentarian north of the Border.
Yesterday he said that Scotland was "lovely" because it was not "full of people".
Asked about the SNP's plans for separate immigration policies if voters back independence, Mr Coburn said: "Why don't we have more children?"
"Scotland is lovely because it's not full of people. That's why a lot of people love Scotland."
He added: "If the SNP is a nationalist party I'll eat my hat.
"What nationalist party wants to import lots and lots of people into the country and change the nature of it?"
Mr Coburn, who is gay, also said he supported civil partnerships but was opposed to the introduction of same-sex marriage as he believed that it would "breed homophobia".
He added: "I don't see the point in crossing the road to pick a fight with people of faith."
Marco Biagi, the Edinburgh Central SNP MSP, said that Mr Coburn's comments were reminiscent of the kind of communist rulers who urged their citizens to breed "in some sense of patriotic fervour".
He also called on Mr Coburn, who was born and educated in Glasgow but who has been based in London in recent years, to "connect with real Scotland".
Following his election Mr Coburn announced that one of his main aims was to do himself out of a job.
He said that in Brussels he had two main aims, to highlight what he said were the problems of the European Union and "to make myself redundant".
Ukip received more than 140,000 votes in Scotland in the European elections. The SNP and Labour took two seats each, and the Conservatives and Ukip one each.