The Mediterranean islands of Malta and Cyprus both offer their own versions of the scheme and concerns have been raised in Brussels that EU members are marketing European citizenship.
Last year Russian oligarch Oleg Deripaska became the latest high-profile tycoon to buy a Cypriot passport, according to the Guardian, which allows him visa-free access to the EU.
Deripaska, an aluminium magnate with connections to Donald Trump’s former campaign manager Paul Manafort, became the latest member of the Russian elite to purchase a Cypriot passport and fears are growing among other EU nations that passport candidates are not being vetted thoroughly enough.
Portuguese MEP Ana Gomes has described the visa scheme as “absolutely perverse, immoral and increasingly alarming”.
She added: “Cyprus is the biggest European investor in Russia and a great number of Russian nationals acquired Cypriot passports.
“We are all aware that there is also a big problem of recycling money. The point is that Cyprus, like other countries, is not just selling its passport. It is marketing European citizenship.”
The European Commission, which is headed by Jean-Laude Juncker, launched an inquiry into citizenship-by-investment programmes in the EU last year following Cyprus’ decision to make it easier for rich foreigners to gain citizenship in 2016.
Until September 2016, foreign investors had to have at least €5million (£4.45million) in domestic assets, including real estate, firms and government bonds.
Cypriot officials then decided to lower the threshold to €2million (£1.78million).
In Malta, prospective investors must shell out €650,000 (£577,000) for the main applicant, as well as €25,000 (£22,000) for a spouse.
Applicants are required to buy a house worth at least €350,000 (£311,000) and there are also hefty application and due diligence fees, as well as a mandatory investment of €150,000 (£133,000) in financial instruments approved by the Maltese government, to be held for a minimum of five years.
Naomi Hirst, a senior campaigner at Global Witness, said those EU states which sell citizenship should carry out “the sharpest of checks” on applicants.
“The source of wealth and background of these individuals should be scrutinised,” she said.
“If not, then the whole of the EU could be made vulnerable to those who will use these schemes as a ‘get out of jail free card’ to move freely around Europe.”