He also described himself as an "appropriate immigration man".
The coalition is planning to cap the annual migrant intake at 170,000, well below the peak of near 300,000 in 2008.
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Mr Abbott was asked about his views of late 2008 when he said one of the Howard government's "greatest but least recognised achievements" was to rehabilitate the immigration program to record levels.
"Public support for the program increased at the same time as the numbers increased," he told the Nine Network on Sunday.
"One of the reasons for that was the Howard government stopped the boats."
Public support for immigration was falling away now because the government had not been able to control Australia's borders.
Mr Abbott also was challenged about comments he made in January rejecting a notion that Australia should have a fixed carrying capacity.
At the time he said that "as many people as possible" should be able to enjoy the freedoms and benefits of living in Australia.
Abbott rejects U-turn criticism
Mr Abbott rejected criticism he had made a 180-degree turn in seven months.
"I'm an appropriate immigration man and I want a strong Australia.
"Over time a strong Australia will be a bigger Australia, but not nearly as big as the kind of figures that recent levels of immigration would give us."
Australia did not need 43 million people by 2050, Mr Abbott said.
Parental leave scheme questioned
Meanwhile the federal government has shed doubt on Mr Abbott's parental leave scheme.
Minister for the Status of Women, Tanya Plibersek, says Mr Abbott submitted savings of $20 million to the Department of Finance and Administration on Friday which should be used to implement the paid parental leave scheme on January 1.
Mr Abbott couldn't claim these savings if he intended to implement the scheme, she said.
"Mums and dads are particularly worried because they remember him saying, `paid parental leave: over this government's dead body'," Ms Plibersek told reporters in Sydney on Sunday.
"Not so long ago Tony Abbott told us you couldn't believe what he said, he said he wasn't always speaking the gospel truth.
"Today he's admitted being kept on a short leash for the rest of the campaign.
"So the fact that he's said that you can't always trust what he says, that he's on a short leash for the campaign, he's claimed $20 million worth of savings for implementing paid parental leave, he won't say when his scheme will start: it all adds up to no paid parental leave for Australian mums and dads."
