Victoria's busy emergency departments would be flooded with an extra 10,000 people a year if the Abbott government's $5 GP co-payment goes ahead in July, state government modelling shows.

One day after the federal government dumped its cut to the Medicare rebate for short GP consultations of $20, the Victorian government stepped up its attack on the broader $5 co-payment for all GP visits, due to start on July 1.

Deputy Premier James Merlino says modelling shows 10,000 extra patients a year will flood Victorian emergency departments under a $5 GP co-payment. Credit:Wayne Taylor

Deputy Premier James Merlino said modelling showed the $5 co-payment would deter many Victorians from visiting their GPs because they could not afford it, making them sick enough to need hospital emergency care.

"As it is, we know that around 7 per cent of sick people delay going to a GP due to cost… Our modelling shows that 10,000 people each and every year will be forced to go to an emergency department because of Tony Abbott's GP tax," he said.