The new gates use facial recognition to match the faces of UK and EEA passport holders with their biometric passports.
But the e-passports, which contain an RFID chip, could be vulnerable to attack, claimed security specialist Ken Munro.
"As yet, cloning seems to be the most pressing issue however, future attacks could lead to passport forgery, or even modification over the air. If someone could replace the photo, then a forged passport could be used to beat the system," he said.
Ken Munro, director of Secure Test, said that the timetable for issuing the UK biometric passport, first available in March 2006, is so tight that fraud prevention technology is unlikely to be developed quickly enough.
"Seven million vulnerable passports are being issued per year. It will be a long time until new technology that prevents hacking attacks can be rolled out. US e-passports include a layer of foil in the lining to prevent RFID skimming attacks UK passports do not."
A home office spokesman said of Munro's claims, "The first thing to note is this is a trial, the system has been tested in the sense that it is already used in other countries such as Portugal and Singapore, and the system will not function as a standalone check, there will still be staff making checks at the border. Security is something we constantly review."
The "e-Borders" electronic border system aims to ensure every visitor is counted in and out of the country by 2014.
More than 99% of foreign nationals from outside the EEA will be tracked in and out of Britain by 2010, according to the Home Office.
If successful the gates could be rolled-out across the country.