The new MG 3 has been priced at £18,495, making it the cheapest full hybrid car on sale in the UK, ahead of the Renault Clio and the Toyota Yaris.
MG has also revealed specification details for the supermini, which is open for order now with deliveries set to begin imminently.
Its new Hybrid Plus powertrain – MG's first non-plug-in hybrid offering – combines a 101bhp 1.5-litre four-cylinder petrol engine with a 107bhp electric motor to give a combined 192bhp and 313lb ft,
That makes it markedly more potent than the Clio and Yaris hybrids - and quicker too, with a 0-62mph time of 8.0sec.
Whereas the old 3 variously offered a five-speed automated manual or four-speed automatic gearbox, from launch the new car drives its front wheels through a three-speed auto, with a manual option coming later.
MG touted the performance benefits of this system "over the commonly used CVT transmission often found in hybrids", claiming its three-speeder avoids lag to give more responsive acceleration. For reference, the CVT-equipped Yaris needs 9.2sec to complete the 0-62mph sprint.
The extra poke doesn't come at the great expense of efficiency; MG claims the 3 will offer a combined 64.2mpg – almost 20mpg up on its predecessor – and have vastly reduced CO2 emissions, at 100g/km, both figures that stack it up neatly against its French and Japanese rivals.
The hybrid uses a 1.83kWh battery and gives the 3 enough juice to cover short distances at speeds of up to 50mph with the engine off. MG
Inside, the 3's cabin is an all-out departure from its predecessor, ushering in new 'floating' twin screens – a 7.0in driver's display and a 10.25in infotainment touchscreen – that feature new-look graphics and are more responsive.
The 3 will be sold in two trim levels in the UK. The range opens with the SE, which includes smartphone mirroring, four USB ports and a rear parking camera as standard. The £20,495 Trophy adds faux-leather seats (heated in the front), keyless entry and a 360deg parking camera. All cars get a suite of safety equipment plus Apple CarPlay and Android Auto as standard.
Its wheelbase is now 50mm longer, at 2570mm, which frees up legroom in both rows of seats. More significant is the increase in boot capacity that comes from the longer overall footprint: at 298 litres, the 3 now has one of the largest boots in the segment.
MG previously told Autocar its reinvented 3 can claim a much higher share of the supermini segment than its predecessor ever did, because the Ford Fiesta is no longer around to claim the lion's share of sales.
The new 3 arrives – with the option of hybrid power for the first time – around six months after Ford axed the Fiesta, historically the best-selling small hatchback and often the overall best-selling car in the UK.
Ford's exit from the segment, together with the MG's extensive technical and visual overhaul, could have huge implications for the MG's potential success, and indeed the company's product planning boss David Allison expects to sell 10,000 examples of the new 3 per year in the UK - nearly three times the sales of the previous car in its best year.
"A very iconic car has disappeared, and I think there's a great opportunity for someone to come and sweep up for those people that don't necessarily want an SUV and still want a 4.1-metre supermini that pretty much ticks all the boxes," he said.
"I don't think we will pick all of it up, but I think it will give people a choice, and that's important. The B-segment isn't where it was in terms of the model choices that are available, and you've only got to look at the rise of the SUV and the decline of the B-segment to see what's been happening."
The new 3 is expected to cost around £18,000 in hybrid form and as little as £16,000 in pure-petrol guise with a manual gearbox - with bosses planning for it to have a roughly 10% price advantage over both its pure-ICE and electrified rivals.
Making the 3 as accessible as possible is important, Allison said, because "it gives us a point of difference, and that's important, because while we're very close to being in the top 10, we're still quite invisible.
"People are quite familiar with the [MG] badge, because it's been around for 100 years and their grandad used to drive one and all that good stuff, but I still think there's a lack of recognition of what we sell today. Our job to tell people we exist is still really quite important."
Designed at the firm's Shanghai design studio, taking stylistic influence from the Chinese brand's current crop of crossovers and hatchbacks, the new 3 is slightly longer and wider than its pure-ICE forebear.
It can also be driven in Series mode – with the engine functioning as a generator – or as a parallel hybrid, where the two power sources work in tandem to give the full 192bhp output.
The firm also said that its engineers in China and Europe have collaborated to ensure the 3's dynamics are fine-tuned for the requirements of various global markets and that as a result it "offers a refined drive but keeps MG's 'fun to drive' ethos at its core".
Precise details of its chassis are thin on the ground, but MG said it benefits "from the use of new ultra-high-stiffness components" and that the suspension has been made lighter and tuned to give higher grip.
It also delivers "new highs in refinement and noise suppression", apparently, courtesy of optimised engine mounts and new sound-absorbing materials throughout the chassis.
