"We are suing the British government for the killings and atrocities their soldiers committed between 1894 and 1899 as they tried to force their rule on the Bunyoro-Kitara kingdom," Ernest Kiiza, the speaker of the kingdom's parliament said.
"What they did is worse than what Usama bin Ladin or Joseph Kony (the leader of the brutal Ugandan rebel group the Lord's Resistance Army) have done," Kiiza said.
These days, the kingdom, much reduced from its original size, is home to about a million people.
Kiiza said it was yet to be decided whether the lawsuit would be filed in a British court or in the International Criminal Court in The Hague.
Kiiza accused British troops of committing mass murder, claiming the kingdom's population had plunged from two million to less than 10,000 after the plunder.
"They captured our king and banished him to the Seychelles for 23 years and though they say that he died as they brought him back, we have since got evidence that he was killed," Kiiza said.
"We were one of the richest kingdoms in this region, but because of the plunder, our people have remained in poverty since then," he said.
Bunyora-Kitira put up a formidable fight against the British and fell only after the neighbouring kingdom of Buganda joined forces with the invaders.