Ministers have no idea what impact the money has had, they warned.
The scale of serious drug addicts has remained stable at around 330,000 since 2004 and they cost society around £15 billion a year, virtually all of which is related to crime.
The Commons Public Accounts Committee said the Government spends £1.2 billion a year tackling problem drug use but does not know how effective measures are.
The MPs also called for more drug addicts to be met at the prison gates to ensure their rehabilitation continues outside jail and signalled the worst addicts may be better dealt with in secure residential units than being returned to their communities.
In a report today, the PAC added that the Home Office did not know whether a cross-Whitehall strategy launched in 2008 reduced the cost of crimes committed by problem drug users.
The PAC found that problem drug users typically relapse several times during or after treatment, and that about a quarter resisted any help at all.
Deaths among problem drug users increased in the past five years, to 1,620 in 2008/9.
Edward Leigh, chairman of the PAC, said: "Given the amount of public money being spent, it is unacceptable that the Home Office does not know what overall effect this spending is having.
"It does not carry out enough evaluation of its work and does not know if its drug strategy is directly reducing the overall cost of drug-related crimes.
"It is of particular concern that measures to cut problem drug use by young people are having limited effect.
"Preventing the young from descending into problem drug use is an essential part of bringing down the number of problem drug users in future."
The scale of serious drug addicts has remained stable at around 330,000 since 2004 and they cost society around £15 billion a year, virtually all of which is related to crime.
The Commons Public Accounts Committee said the Government spends £1.2 billion a year tackling problem drug use but does not know how effective measures are.
The MPs also called for more drug addicts to be met at the prison gates to ensure their rehabilitation continues outside jail and signalled the worst addicts may be better dealt with in secure residential units than being returned to their communities.
In a report today, the PAC added that the Home Office did not know whether a cross-Whitehall strategy launched in 2008 reduced the cost of crimes committed by problem drug users.
The PAC found that problem drug users typically relapse several times during or after treatment, and that about a quarter resisted any help at all.
Deaths among problem drug users increased in the past five years, to 1,620 in 2008/9.
Edward Leigh, chairman of the PAC, said: "Given the amount of public money being spent, it is unacceptable that the Home Office does not know what overall effect this spending is having.
"It does not carry out enough evaluation of its work and does not know if its drug strategy is directly reducing the overall cost of drug-related crimes.
"It is of particular concern that measures to cut problem drug use by young people are having limited effect.
"Preventing the young from descending into problem drug use is an essential part of bringing down the number of problem drug users in future."
