Vauxhall is aiming to offer class-leading low CO2 and fuel consumption in a new version of the Insignia due in September.

Using a 140bhp variant of the 1.4T engine already offered in smaller Vauxhall models, the new version is expected to have CO2 emissions of 129g/km in hatchback and saloon guises and official fuel consumption of 51.4mpg on the combined cycle.

Currently the 122bhp Volkswagen Passat 1.4 TSI saloon has CO2 emissions of 138g/km and fuel consumption of 47.9mpg on the combined cycle, while the lowest CO2 emissions available in a petrol Ford Mondeo is 149g/km for the 160bhp 1.6 Ecoboost stop/start, which achieves 44.1mpg.

It would mean the Insignia 1.4T is two BIK tax bands lower than the Passat, and six lower than the Mondeo.

The Insignia 1.4T will offer the lowest BIK tax liability in the range with the exception of the Ecoflex diesel models. For example, a 20% taxpayer in the the entry-level Insignia 1.4T ES could expect an annual BIK tax bill of £559 compared with £700 for the standard Insignia 2.0 CDTi ES, while fuel consumption on that model is 56.5mpg on the combined cycle.

The annual BIK tax for a 20% taxpayer in the new 119g/km Insignia Ecoflex stop/start is £509.

The move should help make petrol models more appealing to lower mileage company car drivers and could also influence decisions if tougher emissions rules leads to a higher premium for diesel engined cars.

P11D prices for the new Insignia 1.4T are expected to start at £18,625.