The change is designed to make it harder for estranged parents to abduct their children and take them abroad.

Figures for 1997 show there were 230 abduction cases involving 338 children.

Children already on their parents' passports can continue to travel on them until they are 16 or the passport expires, but children going abroad for the first time will now need separate documentation.

Fees for children's passports, valid for five years, were reduced in March from £18 to £11 for postal applications.

The Home Office Minister, Mike O'Brien, said: "This move will improve security, make child abductions more difficult, facilitate travel and maintain the Passport Agency's efficiency and effectiveness.

"In due course all children should hold their own passport."

A spokeswoman for Abta, the Association of British Travel Agents, said the move was not expected to cause undue inconvenience for travellers.