The glasshouse will be planted with a mix of speciality tomato varieties, and is expected to be operational by October.
Fitted with the latest in horticultural equipment and technology, it will be thermally-linked to the other greenhouses on site, enabling heat generated by the combined heat and power (CHP) units to be exchanged between the houses.
The new glasshouse will also feature sodium grow lights throughout for year-round tomato harvesting. As with the existing greenhouses, the new facility will employ rainwater capture and biological pest control to maintain environmental credentials.
Thanet Earth completed its fifth glasshouse last year built to grow cucumbers.
The move will bring the number of people working at the east Kent site to around 830.
Thanet Earth managing director Des Kingsley said: "Adding more capacity for British-grown speciality tomato production will make Thanet Earth an even stronger partner for our retail customers.
"Their consumers are huge supporters of UK-grown products and the demand for British produce is expected to increase. The Thanet Earth name is well-known and respected in this regard."