"We're going to speak our own language," he said, without specifying which of the poor west African country's indigenous tongues would replace English.
The 48-year-old Gambian strongman is often pilloried for rights abuses and the muzzling of the press, and members of the diaspora have set up critical news outlets against Banjul.
A video of his latest broadside against Britain, delivered in English during the swearing-in of a new chief justice on Thursday, was uploaded on YouTube.
The country has several languages to choose from as a replacement for English.
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Gambia, a country of about 1.8 million, is a finger of territory flanking the Gambia River, with Senegal on either side and a narrow Atlantic coastline.
In 2008, Jammeh gave an ultimatum to gays and lesbians to leave his country, saying he would "cut off the head" of any homosexual found in Gambia.
Two years later the European Union cancelled USD 30 million of aid because of concerns over human rights and governance issues.
Jammeh said Britain had "no moral platform" to talk about human rights anywhere in the world.
"What brought the British in the first place to Gambia... was trade in ivory because Gambia had a lot of elephants," he said.
"They ended up wiping out the elephants and then turned around and started selling Africans. The British instituted slavery."
"The only thing they left us with is unfortunately the English language," he said.