Mercedes-Benz is expanding its line-up of plug-in hybrids with the addition of the CLA 250 e and GLA 250 e.

The new models, which are expected to arrive in early summer, will join the A 250 e and B 250 e using a 1.33-litre petrol engine and electric motor.

The CLA 250 e Coupe and CLA 250 e Shooting Brake will be available to order from April. The GLA 250 e will be offered a month later, in May.

All versions feature a 15.6kWh battery, enabling a zero-emissions range of 32-42 miles (WLTP) depending on model.

The powertrain develops 218PS and 450Nm; providing 0-62mph acceleration times of between 6.8 and 7.1 seconds.

For the first time on a Mercedes-Benz vehicle, the combustion engine is started by the electric motor - the compact hybrids do not have a separate 12-volt starter.

The battery, which weights 150Kg, accepts charging speeds of up to 24kW, enabling a 10-80% charge in around 25 minutes.

Mercedes redesigned the exhaust system on the plug-in hybrid models to enable smarter packaging of the battery and minimise the impact on boot space. With the rear silencer housed in the transmission tunnel, integrating the fuel tank into the axle installation space creates additional room beneath the rear seats for the high-voltage battery.

The hybrid system uses a route-based operating strategy, taking factors such as navigation data, speed limits and route into account. The operating strategy takes into account the entire planned route and prioritises the electric driving mode for the most sensible route sections in each case.

UK pricing and specification for the CLA and GLA plug-in hybrids is still to be confirmed.