The model will launch as part of plans to grow GS sales to 2,500 units in 2014, of which 60% are predicted to be conquest buyers according to Toyota GB president and managing director Jon Williams.

'We're going to be supported in our aspirations by the introduction of a low displacement hybrid GS in the second half of next year,' he said at the car's press launch this week.

The fourth generation GS arrives in the UK this June with a choice of either a 2.5-litre petrol or hybrid drive, which uses a 3.5-litre petrol engine. No diesel version will be offered.

At 137g/km, the most efficient GS 450h is the lowest-emitting petrol hybrid on its class. But in carbon-taxed Europe it lags behind diesel models on CO2 emissions, with several now under 120g/km and the E-Class hybrid, which emits 109g/km in its most efficient form.

Williams said despite 20% of executive buyers considering hybrid technology for their next car, taxation meant lowering the GS's CO2 output would be important in a segment where 80% of new cars have a diesel engine.

'In the E segment, CO2 is essential because the majority of drivers in that segment have company cars,' he explained.

Few details are available yet, but the small hybrid looks likely to be a four-cylinder petrol and would need to come in well under 120g/km to steer buyers away from diesel engines. Especially in the corporate market once the BiK surcharge for diesels, which favours hybrid models, is removed in April 2016.

Diesel-rivalling hybrids have performed well for Lexus in the UK. Over half of its 8,269 sales last year were the CT 200h compact, which has given the carmaker a much-needed footprint in the premium c-segment, aided by its 94g/km CO2 emissions.