A Department of Human Services phone line is telling callers that changes to Medicare, including the new $7 GP co-payment, are set to apply from July 2015.

But callers to the Department of Human Services Medicare program have heard a pre-recorded message saying the changes will take effect from July 2015.

The message says: “From the first of July 2015 the Medicare benefit will be reduced by $5 for all patients for non-referred general practitioner consultations, out-of-hospital pathology episodes [and] out-of-hospital diagnostic imaging services.”

The recording also suggests the controversial $7 GP co-payment has also already been approved.

“Patient contribution of $7 will be introduced and this may be charged by the provider.”

The message has been posted even though the Government has not yet introduced the laws required to enact the change.

A spokesman for Human Services Minister Marise Payne said the “intent of the message … is to inform customers of the proposed change”.

“After every budget, it’s routine for the department to communicate proposed changes that may affect our customers,” he said.

The spokesman said “routine communications such as these are organised and written by the department” and have been used for previous budget measures.

Federal Opposition Leader Bill Shorten used his first question in Question Time to target the issue, asking Prime Minister Tony Abbott for an explanation.

“Is this Prime Minister so arrogant that his Government is telling people that they will have to pay his GP tax when it hasn’t even passed the Parliament?” he said.

Mr Abbott replied that it was the Government’s intention that Parliament will support the measure to make Medicare “sustainable for the long term”.

“Madam Speaker, it is the Government’s intention that there will be a GP co-payment from the middle of 2015,” he said.

Labor contested the Prime Minister’s reasoning, saying the $7 fee was not going towards offsetting Medicare’s costs, but towards a new medical research fund.

When the legislation is finally introduced, it is expected to pass the House of Representatives and go straight to the Senate.

The Coalition will need six crossbench Senators to vote in favour of the proposal.

The Opposition and the Greens both oppose the measures announced in the budget, and Palmer United Party leader Clive Palmer has already stated that his loose alliance of PUP and independent Senators will also oppose the changes.

It is not clear how long the message has been running on the Department of Human Services line, the contact number for Australians looking for information on welfare including Centrelink.