Porsche is poised to give the green light to a direct rival for the BMW 5-series and Mercedes E-class after more than a year of research and debate, according to company insiders.

If the project is rubber-stamped, Porsche would for the first time be entering a mainstream market segment, albeit a premium sector dominated by the German ‘big three’. If the model gets the go-ahead, it will hit showrooms in 2016 at the very earliest, but it is still considered part of Porsche’s plan to sell 200,000 units annually by 2018.

Michael Mauer, Porsche’s styling chief, was recently quoted as saying that a road car smaller than the Panamera “was a possibility”. It’s thought that Mauer’s design team have recently been able to spend serious time on the 5-series-sized concept, now that the Macan SUV and Panamera facelift are both heading for the showroom.

Most expect that the ‘Pajun’ (a nickname derived from ‘Panamera junior’) will be a five-door fastback, like its bigger brother. A Mercedes CLS-style sportwagon version is also pencilled in, with a two-door coupé possible in the next decade. It’s also thought that V8 and four-cylinder engines have been ruled out.

Most industry sources expect the Pajun to be built on the VW Group’s next-generation MSB platform. Porsche is developing this rear-drive and all-wheel-drive architecture for use under the next-generation Panamera, Nearly all future Bentleys, among other high-end VW Group models, will also use it. 

Porsche could have used Audi’s next-generation mixed-materials MLB architecture, which will also underpin its upcoming Macan SUV, as well as all future Audi models from the A4 to A7.

However, the MLB is a natively front-wheel drive platform, so all versions of an MLB-based Pajun would have been all-wheel drive. A front-wheel-drive Porsche is considered unthinkable.

According to figures from IHS and Credit Suisse auto analysts, the global market for premium E-segment cars — which includes the 5-series, E-class and Audi A6 — will this year be about 970,000.

That figure is projected to bounce along at about the same level until 2017, when a growth spike will take it to about 1.3 million units by the end of 2019. So this is fertile new territory for Porsche.

This market segment promises substantial profit margins. It’s not as profitable per unit as the market for big, premium SUVs (which Porsche is already exploiting with the Cayenne), but sales volumes are bigger. This is why Maserati is also looking to exploit this market with its new Ghibli.

It’s easy to understand why the more exclusive premium brands see the potential to shake up a segment dominated by the 5-series, E-class and A6. These three models account for about 70 per cent of global sales in the sector.

The premium E-segment market is “underperforming” compared with other premium segments, according to Credit Suisse analyst George Galliers.

“We believe this is part of the ongoing trend towards ‘other’ vehicles [such as SUVs],” said Galliers. “The growth opportunity in this price range/vehicle size is likely to come from comparable products which do not conform to the traditional three-box saloon, in our view. Presumably, this is the opportunity which Porsche also sees.

“We presume that any product which they would offer would most likely have a hatchback configuration as per the Panamera.”