Australian shoppers would have to pay a $5 tax on every parcel posted from overseas under a federal government plan to cover skyrocketing security screening costs.

Parcels containing purchases like clothing, makeup and books worth less than $1000 - which now represent 90 per cent of deliveries entering Australia - would attract the new tax.

The Department of Home Affairs proposal will provoke opposition from online retailers like eBay and Amazon, as well as delivery providers who have warned the full cost would passed on to consumers already preparing to pay GST on small online purchases from July 1.

A discussion paper obtained by Fairfax Media shows department is considering ways to balance the bio-security budget, which is under pressure by the explosion in small parcels entering Australia from overseas retailers. Some 38.7 million parcels worth under $1000 each were imported to Australia last financial year - a 22 per cent increase on the previous 12 months.