Lerner was born on October 28, 1903 in Bessarabia (territory now in Ukraine or Moldova). He grew up in a Jewish family, which emigrated to Great Britain when Lerner was three years old. Lerner grew up in the LondonEast End. From the age of sixteen he worked as a machinist, a teacher in Hebrew schools, and as a businessman. He entered the London School of Economics in 1929 where he would study under Friedrich Hayek. A six-month stay at Cambridge in 1934–1935 brought him into contact with John Maynard Keynes. Lerner married Alice Sendak in 1930; they had twin children, Marion and Lionel, in 1932.
Lerner developed a model of market socialism, which differed form the pure planned economy. It became known as the Third Way. By the 1960s Lerner began to distance himself from his early work on socialism.
Lerner developed the concept of distributive efficiency, which shows that economic equality will produce the greatest total happiness with a given amount of wealth.