Britain's consumer watchdog is investigating daily deal site Groupon's advertising practices for allegedly failing to conduct promotions fairly and exaggerating savings claims.

The Advertising Standards Authority has formally investigated — and upheld — complaints against the daily deal site's advertising on 11 occasions and informally resolved 37 cases.

It said Friday it decided to refer complaints to the regulator, the Office of Fair Trading, because it is "better placed" to address underlying issues about Groupon's trading practices.

"We are taking this approach because, given Groupon's track record, we have serious concerns about its ability to adhere to the Advertising Code," the standards authority said in a statement.

The complaints concern Groupon's failure to conduct promotions fairly, failure to provide evidence that offers are available and exaggeration of savings claims.

The Office of Fair Trading said it had opened an investigation of its own into Groupon's trading practices in July.

It said the probe is looking into whether Groupon is complying with consumer protection legislation, and is also considering the concerns raised by the Advertising Standards Authority.

Groupon spokeswoman Heather Dickinson said the company was cooperating fully with the OFT to ensure consumers' rights are protected.

"We are constantly evolving business process to ensure customers receive the best possible experience at the highest standards," she said in an emailed statement.