Russell Zimmerman from the Australian Retailers Association.

Russell Zimmerman from the Australian Retailers Association. Photo: Arsineh Houspian

THE Australian Retailers Association is predicting Sunday will be the biggest day of online shopping in the nation's history as shoppers bombard web-based sellers with last-minute Christmas orders.

Association executive director Russell Zimmerman said a predicted 2.3 million visits to eBay were predicted for this Sunday, a 26 per cent visitor increase on 2011's busiest day - December 11.

''This shows both Aussie shoppers and retailers are racing to the online space as part of a multichannel Christmas shopping experience,'' Mr Zimmerman said.

And the chief executive of the Canberra Business Council, Chris Faulks, said stores that did not have an online presence were already behind.

''Everyone needs to realise that the upsurge in online purchasing and e-commerce is not just a fad that will go away - this is a structural change for retail purchasing, and it's here to stay,'' Ms Faulks said.

She said it was a fantastic way to compare prices.

''I'm buying a large amount of my Christmas shopping online. It's convenient. I can do it out of hours and it's often cheaper. It is how people compare prices and purchase. That's not to say bricks-and-mortar stores aren't important, but increasingly retailers will have to look at e-commerce to grow.

''I compare it to the change from horse and buggy to motor vehicles - there isn't any going back.''

ACT retail sales figures, released this week, showed a 2.2 per cent decline in October.

Ms Faulks said local retailers were hoping Canberrans would start spending in the next two weeks.

The Australian Competition and Consumer Commission has also released an app to help buyers with their holiday purchases.

It clarifies the laws around online refunds, returns, warranties and lay-by as well as storing photographs of receipts.

Deputy chairwoman of the commission, Delia Rickard, said the app takes the worry out of Christmas shopping as often Australians are confused about their rights.

''If products don't work as promised, or don't work at all, you have rights as a consumer regardless of whether you bought it online, in a shop, full-price or on sale,'' Ms Rickard said.

The free app is compatible with Apple and Android smartphones and tablets.