A glaring failure by almost all European countries to check passports against an international database of lost and stolen travel documents is leaving the Continent vulnerable to a terrorist attack on the scale of the Madrid train bombings, the head of Interpol has warned.
In what he said he hoped would not be his "last interview", Interpol's Secretary General Ronald Noble said nearly all EU members fail to make crucial checks against the agency's database of 15 million suspicious passports - allowing potential terrorists to enter Europe and cross multiple borders undetected.
"So many basic steps aren't being taken, which could lead to another September 11, another July 7 (the 2005 London Underground bombings), another March 7 in Madrid," Mr Noble said.
Speaking almost two decades after a terrorist used a stolen Iraqi passport to enter the US and bomb the World Trade Center, killing six people and injuring 1,042, he added: "The lesson that should have been learned is that people carrying stolen travel documents, if they are not stopped, can enter your country and mastermind a horrible attack."
The former head of the US Secret Service also revealed that last year 500 million flights were not screened against the Interpol database.
Mr Noble said the Schengen Agreement, which allows people to travel across much of the EU without a passport, meant that a single soft spot in border security could put the whole of mainland Europe at risk.
"If we all say that we are going to trust one another to screen and control people coming through our borders then we should all have the same standard," the Interpol chief said.
"Right now, there are less countries than fingers on my hand in the EU that are systematically screening the passports of people coming across their borders through Interpol's database.''
A European Commission source said the Schengen area had its own database of documents for checks on all external borders. "Schengen member states are not obliged to carry out systematic checks against the Interpol database," he said.
However, Interpol maintains that the Schengen system is not as comprehensive as its own database, as it excludes records from 131 non-EU countries that also contribute to the Interpol logs.
The UK Border Agency acknowledged the importance of the Interpol system, saying its own high usage of the database was "indicative of the seriousness and priority we place on border security".
Britain is the only EU country to systematically check passports against those registered as missing worldwide.
Last year over 11,000 people were caught trying to enter on lost or stolen passports. Britain carries out more checks database than the rest of Europe combined.