Members of the public were unable to access the site for hours on the day of its launch last week, after it received more than one million hits per hour. The delays continued, and as Computer Weekly went to press a notice on the site said the public would not be able to search the database for one week because it could not meet public demand.
The site, which features the details of 32 million people who lived in England and Wales in 1901, was designed to cope with up to 1.2 million hits a day.
The site's creator QinetiQ, which was formed from the Defence Evaluation and Research Agency, said the Public Records Office site was a victim of its own success.
The government agency joins a growing list of organisations whose Web sites have suffered glitches or delays when launched.
Internet bank Cahoot crashed on the day it went live, while the Halifax's Internet bank Intelligent Finance was delayed at the last minute after tests highlighted problems with the system's capacity.
A spokesman for QinetiQ said it planned to double the capacity of the database by next week.