The assistant treasurer, Stuart Robert, has blamed “connectivity issues” for charging taxpayers more than $2,000 a month for his home internet.

On Friday, Fairfax Media reported that Robert’s expenses for home internet were 20 times higher than that of other federal parliamentarians. Independent Parliamentary Expenses Authority records confirm his average monthly spending exceeded $2,000 in the most recent quarter.

Scott Morrison responded by asking the special minister of state, Alex Hawke, to inquire into Robert’s internet bill, telling reporters at a press conference in Queenstown, Tasmania, that Australians “want an explanation and that’s why I’ve asked for one”.

In the quarter to the end of June, Robert charged taxpayers $7,222 for a “dedicated data line” at his home on the Gold Coast, including $2,832 in May and $2,705 in April. Since 2017, Robert has charged more than $25,000 for home internet, an average of more than $1,500 a month.

Robert reportedly told Fairfax Media he used “around” 300 gigabytes of data in May and the bill was a result of exceeding his data limit of 50GB and having to pay per gigabyte after that.

He blamed “connectivity issues” for the amount charged to taxpayers but did not say what he used so much data for or which company provided his internet services.

In a further statement on Friday, Robert said his family home “is located a significant distance from the telephone exchange resulting in poor broadband internet connectivity”.

Robert said unreliable internet had “interfered” with his ability to perform parliamentary and ministerial duties and “at the time a 4G home wifi internet connection was the only way to receive reliable and stable internet access”.

“I can confirm that the NBN is now being rolled out in my local area and I have a connection appointment booked in. When installed, this will result in an immediate drop in costs to a level similar to other parliamentarians.”

Robert has a master’s degree in information technology and was the chief executive of GMT Recruitment, an IT recruiter, before he entered parliament in 2007.

He was dumped from the Coalition ministry by Malcolm Turnbull in 2016 after a scandal over a “private” trip to Beijing when he attended an event to celebrate a deal involving an Australian mining company headed by a Liberal party donor.

Morrison appointed Robert assistant treasurer in his August reshuffle after replacing Turnbull as prime minister.

Labor’s communications spokeswoman, Michelle Rowland, told Guardian Australia it was “telling that a member of parliament with such contempt for taxpayer money was elevated by Scott Morrison to the position of assistant treasurer”.

“Stuart Robert needs to explain why taxpayers are forking out thousands of dollars every month for his internet access, when alternative options are available at a fraction of the cost.”

During his time as communications minister in 2014, Turnbull once famously argued that people who wanted to connect to the national broadband network should buy a house where it was available.