The Vixen-based cars were replaced in the early 1970s by the M series. The bodywork was designed by Mike Bigland, who had previously been John Burton‘s racing mechanic. It was a major improvement over the Vixen. It was much cheaper to produce, more durable and offered better protection for the passengers in the event of an accident. Between 1972 and 1980, the car was fitted with a variety of engines. In addition to the 2500M, 3000M, 1600M, Taimar and 3000S models, the V6 had also turbocharged variant. Jack Pickard also returned to the company during the production of the M series. TVR was so confident in their cars that they gave a 5-year guarantee against corrosion. Car exports also increased, with 60% of their cars sold in Europe and the United States.

On January 3, 1975, a fire broke out at the TVR factory. Many finished and nearly finished cars were destroyed. Virtually everything was covered in ash. The damage caused was estimated at £200,000. After the dust and ash had been cleared, the walls were sandblasted. Only 150 cars were produced that year, of which only 20 made it to the United States.

By the end of the 1970s, TVR felt it was time to break away from its previous design. They needed to produce a car that would meet emissions standards, be economical to produce, and could be a successor to the M series. In August 1977, TVR management asked Oliver Winterbottom to design a new two-seater coupé. Ian Jones, formerly of Lotus Cars employee, designed the bodywork. The prototype project initially progressed slowly, but in January, 1979 it was finally road-tested. The car was powered by a Ford 2.8-litre fuel-injected V6. It was called Tasmin, a cross between the female name Tamsin and the Australian Tasman racing series. During the development of the car, TVR had no money to pay its suppliers. Its financial problems were further compounded by the fact that £100,000 worth of M-series cars were seized in the United States at the end of 1979 because they did not meet the required emissions standards. The Tasmin was launched in 1980 and, although it was loved by motoring journalists, it was not a success due to its high price and questionable design. The car’s disappointing sales figures once again brought TVR to the brink of bankruptcy. Martin Lilley thus handed over the management seat to a wealthy TVR buyer, Peter Wheeler.