Large increases in diagnoses of sexually transmitted infections (STIs) were seen among gay and bisexual men last year, according to figures published today.
High levels of unprotected sex probably accounted for most of the rise, although better detection of gonorrhoea may have contributed, said a report by Public Health England (PHE).
The report says the impact of STIs remains greatest in young heterosexuals under the age of 25 and in men who have sex with men (MSM).
Large increases in STI diagnoses were seen in MSM, including a 46% increase in syphilis and a 32% increase in gonorrhoea.
Dr Gwenda Hughes, head of STI surveillance at PHE said reducing this spread of the infections "must be a public health priority".
While reproductive health charity Marie Stopes warned that young people are being let down because "we refuse to take sex education seriously in this country".
The total number of new cases of STIs diagnosed in England decreased by 0.3% compared with 2013 - dropping to 439,243 from 440,707.
Of the new cases, the most commonly diagnosed were chlamydia (47%), genital warts (first episode) (16%), gonorrhoea (8%) and genital herpes (first episode) (7%).
Between 2013 and 2014, there was an increase in diagnoses of infectious syphilis (33% - 3,236 to 4,317) and gonorrhoea (19% - 29,419 to 34,958). During the same period, diagnoses of non-specific genital infection fell by 5%, consistent with the decline reported since 2012.
Dr Hughes said: "We are particularly concerned about the large rises in diagnoses among gay men. In this group we saw a 46% increase in syphilis and a 32% increase in gonorrhoea. Gonorrhoea in particular is becoming harder to treat as new antibiotic resistant strains emerge.
"Health promotion and education to increase risk awareness and encourage safer sexual behaviour remain the cornerstones of STI prevention. Ensuring easy access to sexual health services and STI screening is a vital component in the control of STIs.
"Effective commissioning is critical to improving STI prevention. Prevention work should continue to focus on people in the groups at highest risk of infection, such as young people and gay men."
Chlamydia, the most commonly diagnosed infection is easily transmitted, often symptomless and, if left untreated, can put men and women at risk of serious health problems, including infertility.
Genevieve Edwards, director of policy at Marie Stopes UK, said she was concerned the National Chlamydia Screening Programme is "petering out in many areas".
Se said: "In England, the under-25s continue to bear the brunt of sexually transmitted infections, in part because we refuse to take sex education seriously in this country.
"Without a sustained focus on targeted screening for young people, we risk losing the gains made by the national programme altogether.
"We have a twofold responsibility to young people; to give them the knowledge and support they need to guard against infection, and to ensure speedy diagnosis if they need it. Currently, too many of them are being failed on both fronts."
PHE recommendations include annual screening of sexually active under-25-year-old men and women for chlamydia, as well as on change of sexual partner.
MSM should have a full HIV and STI screen at least annually, or every three months if having sex without a condom with new or casual partners.
Black African men and women should have a regular full HIV and STI screen if having condomless sex with new or casual partners, the report says.
Dr Michael Brady, medical director at the Terrence Higgins which supports people with Aids and HIV, said: "We agree with PHE's assertion that a reduction in STIs must be a public health priority. Fundamental to this is effective Sex and Relationships Education (SRE).
"Our new Government needs to urgently ensure that all young people have access to realistic SRE that reflects the realities of their lives – sexuality, STIs, testing."