Apple iPad Pro leaked render
A render leaked on Twitter claims to show the upcoming iPad ProOnLeaks

Apple is working on an iPad with a 12.2in screen, making it the company's largest tablet yet, according to rendered images of the new gadget leaked online.

Rumoured for months but not yet seen in public, the tablet - dubbed iPad Pro - will blur the lines between Apple's iPad and MacBook ranges in a bid to enter the professional tablet market currently occupied by Microsoft and its Surface Pro.

Published on Twitter by reliable technology tipster Steve Hemmerstoffer, the image is from December 2014 showing the iPad's back and sides, which appear to be made from the same aluminium as the iPad Air 2 and a USB Type C port, the same as the new 12in MacBook and replacing the Lightning connection of previous iPads.

The iPad Pro is expected to be powered by Intel's latest line of processors, known as Broadwell, which are estimated to arrive in time for Apple's annual WWDC developer conference in June. This is where the new iPad is expected to debut, alongside an updated 15in Retina MacBook Pro, also packing the new processors.

According to the render, the iPad Pro will measure 223 x 306 x 7.2mm, compared to the 169.5 x 250 x 6.1mm of the iPad Air 2, which has a 9.7in display. Four speaker grills can be seen on the render, although given the extra processing power of the Pro model, two of them could well be for cooling rather than emitting sound.

Apple currently sells iPads in two sizes, the 9.7in iPad Air 2 and the 7.9in iPad mini 3. The iPhone 6 Plus comes next, at 5.5in, while the smallest laptop is the entry-level MacBook Air, which measures 11.6in.

WWDC kicks off in San Francisco on 8 June and will begin with a keynote led by Apple CEO Tim Cook, It is here we will see updates to the company's iOS and Mac software, as well as any new hardware, such as the iPad Pro.