Ginetta Cars announced the development of the G55 in November 2010 as an evolutionary update to the Ginetta G50, which was a GT4-class car. The G55 was designed to supplement rather than replace the G50, providing a more powerful alternative for sports car competition. Upon its release in February 2011, the car was positioned as both a standalone purchase for £75,000 and an upgrade package for existing G50 owners for £25,000. The introduction of the car led to the rebranding of the Ginetta G50 Cup as the Ginetta GT Supercup.
The G55 has been produced in several technical configurations depending on the racing class:
Cup/GT4 Specification: This version features a Ford-sourced 3.7-litre V6 engine. In its initial 2011 Cup form, the engine produced 370 hp and was paired with a 6-speed sequential manual gearbox built by Hewland. By 2020, the ADAC GT4 championship version was specified with a naturally aspirated 3.7L engine delivering 380 PS, with a total vehicle weight of 1,085 kg.
GT3 Specification: Introduced in 2012, the full GT3 variant replaced the V6 with a 4.35-litre V8 engine built by Ginetta Racing. This model utilized wider wheels than the Cup version and retained a Hewland-sourced gearbox.
G55 GTA: This model is marketed in North America as part of a campaign to interest people in American sports-car racing and is also suitable for track day use and high-performance driving education events. It utilizes a 270 bhp (201 kW) 3.7-litre V6 Ford engine with a dry sump and race clutch. It features a 6-speed Quaife helical gearbox with paddle-shifting and auto-blip functionality. The GTA weighs 1,100 kg (2,400 pounds) and reaches a top speed of 140 mph.
The G55 made its competitive debut in the British GT Championship during the Oulton Park rounds of the 2011 season. Four entries competed in the event, with Century Motorsport achieving the best result of the weekend with a ninth-place finish. Century Motorsport later secured the car's highest finish of its debut season, placing fourth at Rockingham Motor Speedway.
In 2011, Rollcentre Racing campaigned a GT3 test mule—utilizing the Cup engine with GT3-specification components—in the Britcar 24 Hours, though the car did not finish. The finalized G55 GT3 made its competitive debut at the Silverstone) round of the Britcar GT series with Optimum Motorsport, finishing eighth overall and third in Class 1. The model's first victory occurred at Donington Park in the Britcar series, where Team LNT and Optimum Motorsport secured a one-two finish for the G55.
In the 2012 Britcar 24 Hours, a G55 GT3 was entered by United Autosports under the Team LNT banner. Driven by Richard Dean, Lawrence Tomlinson, Mike Simpson, and Tom Kimber-Smith, the car finished 21st overall and third in Class 1. For the 2013 British GT season, the field included a G55 GT3 entered by IDL Racing in conjunction with CWS, alongside two works-run cars.
The G55 was announced as one of the official cars for the Project CARS simulator in August 2012, appearing alongside the Ginetta G50 and Ginetta G40 Junior. Ginetta later showcased both the Cup and GT3 models of the G55 at the 2013 Autosport International Show.