Amazon’s algorithms push customers towards more expensive products, according to a new report.

An investigation looking at 250 products over several weeks found that three-quarters of the time Amazon’s own products appeared in the buy box.

A customer would pay 20 per cent more on average if they bought what appeared in the buy box, instead of the same products at the lowest price on the platform, according to ProPublica.

Amazon told the researchers that the algorithms are complex and consider many different factors.

"Vast selection, world-class service and fast, free delivery," a spokesperson told engadget.

In total 94 per cent of sellers chosen for the buy box who did not have the cheapest product were either sold by companies paying Amazon or by Amazon itself.

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Amazon said the algorithm focuses on products where shipping costs do not apply.