Teenage pregnancy rates will rise unless the government takes renewed action, a review for England warns.
The Teenage Pregnancy Independent Advisory Group (TPIAG) warns budget cuts and a major reorganisation of the NHS may threaten the current downward trend in teenage pregnancies.
The under-18 conception rate is at its lowest level for over 20 years.
But experts are warning that a target to halve the teenage pregnancy rate by 2010 will be missed.
Figures for England show there were 38,750 conceptions among under-18s in 2008.
This is a fall of 13% nationally - way short of the 50% promised from the 1998 baseline - although some regions have seen a 45% cut.
The TPIAG is calling on the current government to invest in contraception, sex and relationship education, and for local areas to see it as a priority.
It argues contraception is cost effective, saving the NHS £11 for every £1 invested, in addition to welfare costs.
Local councils and primary care trusts would face much bigger bills if they reduced contraceptive services, it says.
Gill Frances, TPIAG chairman, said: "We warn government that teenage pregnancy rates will rise again unless there is sustained commitment and investment in contraceptive services, along with better sex and relationships education.
"The challenge for local areas is to maintain the current downward trend in teenage pregnancy during major reorganisation in the NHS, the removal of targets and at a time of reduced public spending.
"It is truly shocking to hear about the current level of disinvestment, the loss of posts and projects and closure of contraceptive services."
Some school and college-based contraceptive and sexual health services have already closed, the report says.
A spokeswoman from the Department for Education said: "This country continues to have a higher rate of teenage pregnancy than many other countries and ministers are clear they want to see this reduced considerably.
"Local authorities are best placed to know what works for their communities, and we have seen good examples of local areas reducing their teenage pregnancy rates by tailoring strategies to meet the needs of their local population.
"While the government is having to make some tough decisions, the funding available through the new Early Intervention Grant will give local authorities the freedom and flexibility to set their own targets and decide how best to tackle them."
Julie Bentley of the Family Planning Association and TPIAG member said: "FPA would also urge government to issue revised sex and relationships education (SRE) guidance to ensure that schools are immediately clear about what should be taught."