The US has launched a formal investigation into new digital taxes over concerns they “unfairly target” American tech giants like Facebook.

The inquiry will examine tax schemes in 10 jurisdictions including the UK, European Union and India.

It is the first step in a process that could lead to the introduction of tariffs, or other trade retaliation.

The Treasury defended the UK levy, saying it did not violate “international obligations”.

“Our Digital Services Tax ensures that digital businesses pay tax in the UK that reflects the value they derive from UK users, and is compatible with the UK’s international obligations,” a spokesperson said.

The probe comes as a rising number of countries consider new taxes on online services, arguing that firms pay too little under current law and should be taxed based on where sales or activity takes place, rather than where they are headquartered.

The US, home to many big tech companies such as Google and Amazon, has said the issue should be addressed in a multilateral agreement via the Organisation for Economic Co-operation and Development.

But those discussions have been slow-going, prompting many countries to forge ahead on their own.