Teenagers will be helped to stay with their foster parents until they reach 21 under plans being put to MPs this week.
MPs from all parties are expected to support an amendment to the Children and Families Bill which would fund the cost of people staying with families beyond the age of 18.
The move would help 530 teenagers in England and cost £2.6m a year – which campaigners say is a relatively small amount that would transform the lives of young people. The Government would recoup the costs, campaigners at the Fostering Network said, because fewer young people would be driven to homelessness or offending.
Currently, local authorities fund the cost of children in foster care until they reach 18. At that point, support varies across the country. In many areas, teens are forced to live by themselves at an age when others would remain at home.
Vicki Swain of the Fostering Network said: "This is a once-in-a-parliament opportunity to make a real difference."