Prince Harry's admission of drug taking could threaten his US visa, an American lawyer has warned as he insisted there was 'no exception for royalty'.

The Duke of Sussex revealed in his bombshell memoir 'Spare' and TV interviews that he had taken cocaine, cannabis and magic mushrooms in the past.

MailOnline yesterday told how the Duke is now facing calls for his US visa application to be released to see whether he admitted his drug use before emigrating to California with Meghan Markle in 2020.

A conservative think tank is in the middle of a battle with Washington DC officials who are staunchly refusing to publish any details - including any texts or emails.

The DC-based Heritage Foundation says his visa application must now be released so the American taxpayer can understand whether Harry declared his drug use.

US immigration law has harsh penalties for lying to immigration officials, including deportation and being barred from applying for citizenship.

Former federal prosecutor Neama Rahmani told Page Six last night: 'An admission of drug use is usually grounds for inadmissibility.

'That means Prince Harry's visa should have been denied or revoked because he admitted to using cocaine, mushrooms and other drugs.'