The Immigration Department is struggling to cope with a massive influx of inquiries about the government's changes to the citizenship test, with callers turned away or placed in lengthy queues.
Audio recorded on Monday and obtained by Fairfax Media shows clients are being disconnected and told to "call back later", or otherwise placed in queues of close to 300 people.
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New Zealanders will now have to wait longer to obtain Australian citizenship, prompting criticism from PM Bill English.
It comes after the Turnbull government announced a major overhaul of the citizenship test on Thursday, including the addition of a "values" test, tougher English language requirements and a four-year wait as a permanent resident.
"Due to very high demand we are unable to take your call at this time," worried callers are being told by a machine. "The department apologises for any inconvenience and we thank you for your patience. Please call back later."
The high call volume is affecting callers inquiring about matters unrelated to citizenship – such as holidaying in Australia, employer-sponsored migration and humanitarian visas – who are being told to try again later.
One caller on Monday, who managed to reach the call menu and dial "four" for citizenship, was then placed in a queue of 268 people.
"We appreciate your patience. You are currently the 268th caller in the queue," the client was told, before he ended the call.
A spokesman for the Department of Immigration and Border Protection acknowledged the "significant" spike in calls and said it had devoted extra resources to handling the influx.
"Since the announcement from the government last week, the department has seen a significant rise of inquiries to its service centre," the spokesman said.
"This spike in call volumes resulted in delays for clients calling the department's service centre.
"The department has put in place contingency measures to address the high volumes of calls at this time, including devoting information officers solely to answering citizenship calls."
The department did not answer questions about its average wait times and call duration, or about the average delay faced by customers on Monday.
Announcing the changes on Thursday, Prime Minister Malcolm Turnbull said they would be "empowering" for citizenship applicants.
"This will be good for the applicants, good for the nation," he said.
The elimination of the 457 visa, to be replaced by two types of temporary work visas with new and tougher rules, has led to a flood of inquiries to the department since it was announced last week.
Henry Sherrell, an immigration researcher at the ANU's Crawford School of Public Policy and a former DIBP employee, said it was unsurprising the department and migration agents were feeling the heat.
"There's not much information available so a lot of people are concerned and confused," he said.