The US has sharply limited Hungary’s participation in a visa waiver system for failing to tackle security issues flagged by Washington.

More than a million people have gained Hungarian passports under a fast-track citizenship plan introduced in 2011.

The US says the system, introduced after Viktor Orban came to power, is prone to “security breaches”.

The rules will severely curtail entry rights under the Electronic System for Travel Authorization (Esta).

Those using the system will be allowed one entry, the US embassy in Budapest added. Normally, Esta allows multiple entries for up to 90 days without a visa for tourism or pleasure.

Forty countries are in the Esta scheme. Hungary is the only nation to face restrictions.

The US embassy said the move followed “Hungary’s decision not to fully address the security vulnerabilities created by its earlier implementation of its simplified naturalisation process”.

It added that the US had engaged in “extensive efforts over many years” to resolve what it called “longstanding security issues arising from Hungary’s simplified naturalisation process”.

After Mr Orban became prime minister in 2011, Hungary began offering simplified naturalisation programme to those claiming Hungarian ancestry and living abroad.

The large majority were taken by ethnic Hungarians living in Ukraine, Romania and Serbia.

The vast majority of ethnic Hungarians living abroad support his right-wing Fidesz party, which took 93.89% of the diaspora vote in 2022.

A US official, speaking anonymously to American media, said many of the passports were issued without stringent identity verification requirements. They claimed some of them were granted to criminals who posed a security threat.

Hungary’s interior ministry said that the restrictions put the safety of Hungarians at risk and claimed that Washington was “taking revenge on Hungarians.”

The move comes amid a low point in relations between Hungary and its Western partners.

Mr Orban’s government has frustrated the US and allies with its reluctance to approve Sweden’s bid for Nato membership.

And the EU has consistently raised concerns over democratic backsliding in the country,

Last year, the bloc’s parliament voted to approve a report which accused Mr Orban of creating an “electoral autocracy” which engaged in attacks on press freedom, LGBT rights and the independence of the judiciary.

Budapest rejected the findings and Foreign Minister Peter Szijjarto called the report an “insult”.