Prospective Australians are waiting significantly longer to be granted citizenship, with more people applying and more complex lodgement papers to process.
Wait times for Australian citizenship have blown out by several months, with senior bureaucrats attributing the blowout to a ballooning number of applications and stricter security checks.
The average time from lodging an application to conferral of citizenship has stretched from 12 months in March 2016 out to 16 months this financial year.
Home Affairs officer Luke Mansfield said there were a range of factors behind the increase.
"One is that the department has increased the integrity screening and checking processes from a national security and criminality risk perspective," Mr Mansfield told a Senate committee in Canberra on Tuesday.
"The second factor driving that change is growth in the number of applications. The number of applications has been increasing year-on-year from a very significant base."
Mr Mansfield said the nature of applications coming into the department had also changed.
"There has been an increase in the number of applications from people who arrived some years ago without any form of identity documentation, and the processes around positively establishing identity obviously take quite some time to achieve," he said.
There are almost 210,000 citizenship applications "on hand" as of April 30.
These include lodgements which have not yet been assessed, others that are still being scrutinised, and people who have not yet attended citizenship ceremonies.
Mr Mansfield said there had been a 16 per cent increase in processing staff since July 2016, in an effort to keep pace with demand.