Consular officials can now ask for social media usernames going back five years via a new questionnaire.

It also allows authorities to request email addresses, phone numbers and 15 years of biographical information.

This can be requested when "more rigorous national security security vetting" is needed, a State Department official told Reuters.

According to reports, the State Department expects that about 0.5% of visa applicants will be given the questionnaire.

Critics have argued that the checks could lead to extended, fruitless lines of inquiry or the collection of personal information not relevant to security checks.

Providing the information is voluntary, though the questionnaire informs applicants that "individuals who [...] do not provide all the requested information may be denied a US visa".

A proposal to request "social media identifiers" for travellers using the visa waiver program was put forward by US Customs and Border Protection (CBP) last year.

This came into force for some visa waiver travellers in December 2016.

The new questionnaire applies specifically to visa applicants not using the visa waiver program.

Evaluation of social media activity is increasingly common, though US employers in Maryland and Illinois were recently banned - thanks to state-level legislation - from asking job applicants for their social media logins.