Australian consumers have less than three months until an online shopping tax, as experts warn the "protectionist tariff" will be passed on by businesses without any guarantee taxpayers will benefit.

From July 1, clothing, electronics and furniture bought overseas worth less than $1000 from companies such as Amazon and eBay will be slugged with a 10 per cent GST, as the volume of online shopping surges and local retailers struggle to stay afloat.

Online shopper Ryan McCaugherty. Credit:Nick Moir

It comes as a government inquiry into internet competition led by former deputy prime minister Barnaby Joyce recommends sweeping taxpayer-funded grants for small businesses to make them competitive internationally.

The Turnbull government has already had to revise down its estimates of the new GST takings in the mid-year budget update from $100 million to $70 million following delays in its roll out.