The model will combine advanced hybrid technology with the brand's low-emission Bluetec diesel know-how. Likely to hit dealers in 2009, the 4x4 should emit less than 200g/km of CO2 and return 40mpg. That puts it on a par with the latest C320 CDI.
While there's no official confirmation yet, a senior source admitted: "It's a safe bet that our first move into hybrids will come with the M-Class, using a 3.2-litre V6 Bluetec diesel."
By linking the two-mode hybrid system, developed with BMW and General Motors, Mercedes believes it can eclipse Lexus's trend-setting hybrid SUV, the RX400h. The set-up uses an electric motor in the transmission to reduce weight, improve efficiency and absorb less power.
BMW's M5 is also likely to get the green technology, while the Chevrolet Captiva and Vauxhall Antara are two of GM's candidates for the set-up.