Each bike will be permanently marked with a unique code and added to the national Bike Register database.
If a bike is stolen the security markings enable police to reunite it with its owner. Markings can also act as a deterrent to would-be thieves as the bike is less easy to sell.
Starting this month, security marking will be offered on a first-come, first-served basis at the Bike Doctor marquee, next to the fountain on Commercial Road. Markings will take place between 10am and midday on Wednesday, July 10 and 24, August 7 and 21, September 4 and 18.
The service will also be available at the University of Portsmouth Library in Cambridge Road on October 3 and 31, November 28 and January 23.