The high-profile government campaign to tackle knife crime in big English cities has failed to cut the number of fatal stabbings, according to Home Office figures published today.

The number of teenage homicide victims of knife crime remained unchanged at 23, while the number of adults over the age of 20 killed actually went up during the campaign by seven to 103, results of the official monitoring programme show.

The failure of the £3m campaign to reduce the number of teenagers killed in knife attacks in England's 10 priority police areas is a severe embarrassment to ministers on a highly political crime issue that is likely to dominate the debate on law and order between now and the general election.

Ministers will tomorrow launch a £5m second phase of the "tackling knives action programme" (TKAP) which will see the campaign expanded to 16 police force areas and widened to tackle all forms of serious violence among 13- to 24-year-olds, including gang culture.

Home Office ministers preferred to emphasise the research findings that violent knife crime incidents involving those aged 19 and under were down by 17% during the first phase of the campaign, which ran from July 2008 to March this year.

The home secretary, Alan Johnson, also cited a 32% reduction in NHS hospital admissions for knife crime victims in the 10 target areas.

The Home Office said this compared with an 18% drop in hospital admissions for stabbing injuries outside the targeted areas over the same period.

Controversy has surrounded the knife crime statistics since last December, when the former home secretary Jacqui Smith had to apologise to parliament for the "premature release" of the hospital data when she made public some early results to suggest that the police were making headway against knife crime. Sir Michael Scholar, the head of the UK Statistics Authority spoke out publicly against her "premature, irregular and selective" use of statistics.

The figures published today show that much of the overall 17% reduction in teenage violent knife crime victims is concentrated in some of the biggest cities, including London and Birmingham. But in three out of the 10 police forces involved – Greater Manchester, Nottinghamshire and Thames Valley – violent knife crime went up during the campaign.

The Metropolitan police have had some modest success in reducing the total number of knife crime murders by three, and the West Yorkshire force succeeded in reducing the number of teenage deaths from seven to none during the campaign period. But Manchester saw the number of teenage murder victims of knife crime rise by four and the death toll on Merseyside rose by three.

The number of robberies involving a knife fell by 13% for those 19 and under but rose by 11% for those involving adults.

The campaign included the extensive use of knife arches and wands at pubs, train, tube and bus stations, after-school police patrols and stop-and-search campaigns. More than 250,000 searches yielded 5,469 knives and other weapons.

Home Office statisticians said the overall findings were encouraging, suggesting fewer youngsters were becoming victims. "While caution must be applied when interpreting these trends, TKAP may have contributed to a decline in some measures and persisting reductions in others," said the official research report.

Chief constable Keith Bristow, who is in charge of rolling out the second phase, said "public angst" over knife crime was understandable: "In any crime reduction approach the first thing to do is arrest the increase and turn that cycle around.

"This is a long journey. Success when you're dealing with these sort of problems might be measured in generations, not weeks or months."