The consumer watchdog has written to 62 online retailers after discovering they may not be fully complying with consumer protection laws.
OFT found that some sites had potential breaches of the Distance Selling Regulations (DSRs) and consumer protection laws. The online sweep looked at the websites of 156 online retailers.
OFT discovered that 33% of sites had cancellation policies that which imposed unreasonable restrictions on an online shopper's right to a refund.
Some websites even required that the product be in its original packaging and condition which can make it difficult for shoppers to properly inspect the products.
60% of websites investigated did not provide an email contact address, which is required by the E-Commerce regulations.
Retailers that do not make changes to comply with the laws risk formal action form the OFT or Local Trading Standards Services.
The OFT has created a guidance tool for business online to help resolve some of the key issues found in the sweep. The consumer watchdog has also posted a video online for consumers to better understand their rights when shopping online.
"The OFT recognises that most businesses want to play fair with their customers and to comply with the law," said Cavendish Elithorn, senior director of Goods and Consumer group at OFT. "We encourage all online retailers to check their websites so customers can be confident their rights are being respected when they shop online."