According to a Greenpeace statement, its members "used safety shut-down buttons to cut off power to the assembly line" before handcuffing and chaining themselves to unfinished vehicles on the assembly line at 7am this morning.
Greenpeace says the action is in protest at what is claims are the "climate wrecking" emissions from Range Rovers, Land Rover's premium model.
Land Rover confirmed the incident had taken place but said only a "small part" of the plant was affected.
"The action taken by Greenpeace is both regrettable and damaging - Land Rover is a leading British business and exports over 70% of its production, and contributes significantly to the country's wealth creation," a company spokesman said.
Greenpeace said that although "climate change is the greatest threat the planet is facing" Land Rover "continues to make gas-guzzling vehicles, most of which will tackle nothing steeper than a speed bump".