Porsche is plotting a surprise entry into the electric car ranks with an all-new mid-sized liftback that aims to compete with the Tesla Model S.

Currently in the formative stages of development at Porsche’s Weissach R&D centre in Germany, the secret five-door is planned to form part of a new dedicated fifth model range set to slot into the German car maker’s line-up beneath the Panamera, according to German media reports citing comments made by Porsche’s outspoken chairman, Matthias Müller.

While conventional combustion engine versions of the new mid-sized Porsche model are set to take on established luxury class rivals such as the BMW 5-series, an advanced battery-powered variant is tasked with challenging the Model S on both performance and range in what has developed into an increasingly important global market for electric cars in recent years.

Details of Porsche’s first-ever series production electric car remain shrouded in secrecy, though Autocar understands it has been conceived around a second-generation version of the MSB platform that currently underpins the Panamera.

Set to employ a greater percentage of lightweight, hot-formed, high-strength steel and aluminium than today’s structure, it will boast a shorter wheelbase than that of the Panamera and aim to provide the new car with a kerb weight under the Model S’s 2190kg.

Power for the new five-seat Porsche is planned to come from a state-of-the-art synchronous electric motor. It is likely to provide a similar output to the unit used by the Model S – which offers 416bhp and 443lb ft in its most powerful guise – in a bid to endow the new Porsche electric car with class-leading performance.

The electric motor will draw energy from a yet-to-be-specified battery. Likely to use a lithium-ion process, it is expected to be developed in partnership with Audi, which is currently in the throes of finalising its first-ever electric car, the R8 e-Tron. It is planned to provide the new car with an all-electric range of more than 250 miles/ 400 kilometres.

Porsche has gained electric car expertise through the development of a number of prototypes in recent years, including the Boxster E – an all-electric version of the second-generation Boxster that used a 121bhp electric motor and lithium-ion battery pack.

The new Porsche model forms part of a two-pronged attack being readied by Volkswagen -owned companies against Tesla, whose solid sales growth in recent years has led many established car makers to fast track plans for their own battery-powered models.

While Porsche is targeting the Model S, Audi is set to challenge the soon-to-be-introduced  Model X with an electric variant of its future range-topping Q8 SUV.