The UK competition regulator, Competition and Markets Authority (CMA), is investigating whether Emma breached consumer protection law.
The company is said to use countdown clocks on their website, implying that a lower-price offer will end soon and tricking consumers into making purchases under pressure.
Consumer choice brand, Which? said they have previously warned companies against this in the past.
Rocio Concha, Director of Policy and Advocacy at Which?, said: “Emma Sleep mattresses consistently perform well in Which? testing, so it's disappointing the company is being investigated for the type of misleading sales tactics we have repeatedly warned companies against in the past.
"Which? research has found practices like misleading hurry warnings and countdown clocks can lead to consumers spending more than they intend, as well as feeling manipulated or annoyed.”
The regulator has said the way businesses present information and choices to customers on their websites can be used to influence shoppers’ decisions.
The CMA found that 71 per cent of online shoppers have faced deceiving selling tactics, and the watchdog is calling for businesses to ensure their sale practices are within consumer protection law.
Sarah Cardell, the interim chief executive of the CMA, said the investigation into Emma Sleep was the start of the investigations into misleading online sales techniques.
“The CMA is today reminding businesses they should not use urgency claims to mislead consumers and, if they do, they face the risk of CMA action.”
She added: “Nearly all of us shop online and it’s easier than ever to buy something at the click of a button.
“With the rising cost of living, genuine deals are worth shouting about – but companies using misleading ‘sale’ prices or fake countdown clocks can put unfair pressure on people to buy and could break consumer law.”