Centrelink’s phone system returned 100 engaged signals in three hours when tested by staff of the independent MP Andrew Wilkie.

The agency’s phone system has come under significant criticism in recent years. In 2015-16, about 42% of the 68m calls made to Centrelink were blocked. Another 7.12m calls were abandoned.

The remaining calls had a wait time average of 15 minutes and nine seconds, although the clock is reset when a call is transferred, which happens to 26% of calls on average.

The human services minister, Alan Tudge, said on Monday his government had taken steps to alleviate pressure on the system.

Tudge said his government was “driving the largest improvement program ever undertaken” in Centrelink, citing the introduction of an online claim tracker and a new “virtual assistant”, which he said had answered 95,000 questions since June.

The claim process, he said, was also being streamlined.

“We started with a focus on the student payments, and already we are seeing the processing times for student claims halved,” Tudge said.

“Just this month was the first time we have had a straight-through process of a claim, and by the end of this year about 10% of all claims will be straight-through processed, which means they will be instantaneously done.”

But Wilkie said his office continues to receive calls from constituents who are unable to make it through Centrelink’s call system.

To test the adequacy of the system, Wilkie’s staff called the disability support pension line one afternoon last month.

They received 100 engaged signals in about three hours. Wilkie described the situation as “ridiculous”.

“Imagine how it must feel for someone who urgently needs to speak to Centrelink about their payment and can’t get any assistance on the phone, or face-to-face or online for that matter,” he told Guardian Australia.

“This is an appalling situation and the government must take their fingers out of their ears and fix it.”