France has proposed requiring biometric data from all travellers as they enter the EU's Schengen area.
The French proposal could mean that everyone, including EU citizens, will need to supply fingerprint or facial biometric data to support Europe's Smart Borders systems.
EU civil liberties watchdog Statewatch published the French proposal, which outlines a call to the EC to broaden "the scope of the Smart Borders package for all travellers, also including European nationals".
The letter dated 25 September was sent to the EU's Working Party on Frontiers and was, according to EUobserver, discussed at an interior ministers meeting in Luxembourg on October 8.
The EC proposed the Smart Borders package in 2013 to improve control at the external borders of Schengen member states, which includes most EU states, some non-EU states such as Norway and Switzerland, but not the UK.
As the EC outlines, Smart Borders in conjunction with an entry-exit system and registered traveller programme, would aim to stifle irregular immigration and help flag overstayers and facilitate border-crossing for pre-vetted frequent non-EU nationals travelling to the region.
A subsequent technical study on Smart Borders looked at the potential use of facial image recognition as a standalone biometric or in combination with fingerprints. It also noted issues with the conditions imposed on law-enforcement agencies governing access to biometric data.
The French proposal comes as the EC's Smart Borders public consultation draws to a close on October 29 and coincides with the country's proposed new national-security laws, aimed at boosting government surveillance powers.
According to France, expanding the biometric program to include EU nationals would improve the return on investment on control systems already in place, since non-EU citizens only account for 43 percent of border crossings.
But the main motivation is the threat from terrorists in the Schengen area and nervousness about the influx of refugees to the EU - as well as about EU nationals who join terror groups such as IS.
France said these concerns include "a steady rise in passenger flows, unprecedented migratory pressure and increased terrorist threats, with the specific issue of trips to and from terrorist areas".
The French proposal continues: "Terrorist acts have served as a chilling reminder of the threats posed by certain European nationals or people with the right of free movement upon their return from terrorist areas."
France's proposal would also mean EU nationals would be subject to "systematic verification of their travel document and checks in the databases for stolen, usurped, lost and invalidated documents".