Britain's Home Office has introduced new regulations on passport photographs to bring British passports in line with internationally agreed standards that enable biometric facial recognition technology to work properly.
Facial recognition systems match key features on the holder's face and work best when the face has a neutral expression with the mouth closed.
"If you're smiling or frowning it's not a true representation of what your face looks like," a Home Office spokesman said.
Those posing for passport photographs must also close their mouth, keep hanging hair off their face and not wear a hat, the Home Office said in a guide to the new passport regulations.
Biometric passports, which have already been introduced in Canada and the United States, have been hailed by authorities as an effective tool for fighting terrorism and identity fraud.
New on workpermit.com
workpermit.com's video news and past newsletters are now available in an online archive. The archive is searchable by month and year and goes back to Feb. 2004.