The impetus for the development of the Marina came when Leyland Motors merged with British Motor Holdings (BMH) in 1968, forming British Leyland (BL). BMH was the corporate parent of the two biggest car manufacturers in the UK, Austin and Morris. The new BL management, made largely from ex-Leyland Motors staff, were shocked to learn that apart from the Austin Maxi (then entering the final stages of development) and a tentative design for a replacement for the Mini (the 9X) BMH had no new cars under development. The company's products aimed at the mass-market consisted of the Morris Minor, dating from 1948, and the 1100/1300 range of mid-sized Austin and Morris saloons that were a decade old. BL rapidly implemented a plan to develop a replacement for both the Minor and the smaller Farina models that could be produced as quickly as possible and would be on sale for no more than five years until a genuinely "all new" product could be launched in its place.

The British Leyland Board decided to build the Marina at the ex-Morris Motors plant at Cowley in Oxford, which was largely still as it was in the 1920s. The plant had insufficient capacity – British manufacturers had difficulties in meeting demand in the post-war years – which increased design and production costs significantly, since Leyland had to rebuild the plant.

It was a popular car in Britain throughout its production life, beating its main rival, the Ford Escort, to second place in UK car sales in 1973 and taking third or fourth place (behind the Escort) in other years. The car was exported throughout the world, including North America, and assembled in Australia, New Zealand, South Africa and Malaysia. A total of 1.2 million were built.

According to various sources, the Marina ranks among the worst cars ever made.