That has resulted in the number of people who remain in the country on bridging visas more than doubling in the same period to nearly 230,000.
"Why has the minister allowed for the large blowout in bridging visas and airplane people under his watch?" Senator Keneally asked in the Senate on Tuesday.
In response to the question, government minister Linda Reynolds, who represents Mr Dutton in the Senate, said the increase was a by-product of international students and tourists.
"You might try and get some easy press on this, but the reality is we have a growing number of international students, of tourists coming to our country and that is a great thing," Senator Reynolds said.
"We want all those numbers to increase. As numbers increase, of course you will get an increase in all sorts of categories of people arriving making claims to stay so you would expect that number to grow."
Her question followed Mr Dutton's confirmation that a boat carrying five asylum seekers from Sri Lanka was intercepted in "recent days" and the men sent back.
While the government has trumpeted its success "stopping the boats" since 2013 as a result of its hard line policy of offshore detention and boat turnbacks, the number of asylum seekers arriving by plane has skyrocketed.
Last financial year alone, the number of people applying for asylum who arrived by plane jumped to nearly 28,000, up from 18,290 in 2016-17 and 9,554 in 2015-16.
Chinese and Malaysian applicants account for the bulk of the increase.
While 90 per cent of applications are rejected, many remain in Australia on bridging visas as they exhaust the appeals process which can take years.
Senator Reynolds suggested it was preferable that people seeking asylum arrive by plane, rather than undertake a perilous journey by boat.
"When people arrive illegally by boat they rarely have identification documents, we have no information on them and that means an extended protection claim and legal process."
"In contrast when people arrive by airplane, we have their passports, as well as any other relevant travel documentation. We know who that person is and that allows us to make a quick consideration of their claim.
"In addition, a plane flight is considerably safer than a boat journey."
She said the government has appointed airport liaison officers in transport hubs such as Dubai to offload people who are a "threat".