The suspected plot – to strike parliament when the president and prime minister were inside – was the first of its kind since Poland threw off Communist rule more than 20 years ago and will put scrutiny on radical right-wing groups fiercely opposed to the liberal government.
Prosecutors said the suspect, a scientist who works for a university in the southern city of Krakow, planned to plant four tonnes of explosives in a vehicle outside parliament and detonate it remotely.
The plot had parallels with Anders Behring Breivik, the Norwegian who planted a bomb in Oslo last year and went on a shooting rampage on an island.
"The would-be bomber did not hide his fascination with Breivik. This should not be ignored," Prime Minister Donald Tusk said. "This should be a warning and a good lesson to Poland in the future. This is a new and dramatic experience."
Prosecutors said the suspect, 45, had a small arsenal of explosive material, guns and remote-controlled detonators and was trying to recruit others.