About 40 per cent of Australians are expected to use their smartphones and tablets to shop over Christmas - more than double last year's figure.

Google Australia research has found that there is a 20 per cent increase in shopping related searches year on year and that 40 per cent of all shopping searches now come from smartphones or tablets.

"What we see is we're getting a growth of 20 per cent, year on year, for shopping related searches and mobile devices searches have more than doubled in the last 12 months," Google Australia leader for local and retail Ross McDonald said.

Mr McDonald said with the recent release of the iPhone5 and an increasing number of Australians buying iPads he expected the number of mobile searches to increase more rapidly this Christmas.

"We reckon there will be close to a million new devices turned on between now and Christmas when you think about the iPad launch and the new iPhone launch," he said. "That means there will be more and more Australians using them to make decisions on what they're going to buy for Christmas.

"The last three years the highest number of searches we've had on mobiles have been in the week before Christmas and we estimate that in the week before Christmas this year we will get 50 per cent of our queries through mobile devices."

Mr McDonald said even people who were buying in store still did their research online and used their smartphones and devices to find relevant stores.

"On a big screen people do their product research, then they use a mobile to work out where they're going to go, when the store is open and what offers they have," he said.

He said while some retailers, especially smaller ones, may not be interested in selling online they should still have a mobile friendly website to advertise because that was where most shoppers looked for information about stores and products.

"What we measure is bounce rate and what we see is bounce rates are very, very high if the website is not optimised for a mobile screen," he said.

"If it's not accessible for a mobile, people will very quickly bounce off it and go and look up something else."

AAP