A £5m design studio and technical centre for MG models has opened at the former Longbridge site in Birmingham.
The MG Motor UK complex will become the company's global design headquarters and employ 300 designers and engineers.
The firm said it is a "very significant day and a major new investment in UK automotive engineering and design".
Cars designed there will be sold in the UK and in China. It is the biggest investment at the former plant since the collapse of MG Rover in 2005.
MG Motor UK is a subsidiary of Shanghai Automotive Industry Corporation (SAIC), China's largest automotive business, which owns the MG brand.
In November, the firm said production of the MG6 fastback would move to Longbridge in 2010 after starting in China.
The MGTF sports car is already built there.
The technical centre at Longbridge has been set up by SAIC.
Of the 300 staff at the two facilities, there are 30 designers working on MG models as well as the Roewe brand, which is built in China.
"These two centres of excellence sit at the heart of the MG Birmingham plant where a new family of MG models are currently being designed and engineered," a spokesman said.
"The designing of new cars and the engineering and technical aspects of the cars is all happening here in the UK.
"It's a very significant day.
"SAIC could have gone anywhere in the world for this but they chose Birmingham and Longbridge.
"It's an important endorsement.
"The MG6 fastback will be built here later in 2010 and it will be followed by a saloon version next year.
"They will be both be sold here and in China."
MG Rover went into administration in April 2005 with the loss of 6,000 jobs.
SAIC bought much of the company's intellectual property after its collapse and Chinese rival Nanjing Automobile Group acquired what was left of the MG Rover group.
The two companies merged in 2007.