Home Secretary Theresa May has rejected calls from MPs for a root-and-branch review of drugs strategy, insisting the government's approach is working.
In a recent report, the Home Affairs Committee said a Royal Commission should examine policy and consult the public on alternative ideas.
But she said there was "no case" for such a move and hailed "promising" progress in various areas since 2010.
Early intervention and "recovery incentivisation" schemes were working.
The government has faced calls for a change in approach from campaigners and some police officers amid warnings that existing policies are not working. Speaking last year, former Home Secretary Ken Clarke said the war on drugs was "plainly being lost".
There is growing concern over the growth and prevalence of "legal highs", some of which are banned, amid a recorded rise in deaths linked to their use.
In a recent report, the cross-party Commons committee urged ministers to develop a new series of measures to tackle the harm caused by drug misuse and suggested an independent Royal Commission should take a fresh look at policy and the changing international context by 2015.
While stopping short of supporting a relaxation of legal sanctions for drug use, as previously suggested by experts at the UK Drug Policy Commission, it called on ministers to look in detail at the idea.
'No quick fixes'
Consideration of policy should be "informed by a thorough understanding of the global situation and possible alternative policies", it said.
But in its formal response to the report, Home Secretary Theresa May said the government was already committed to reviewing its drugs strategy every year as well as continuously assessing its effectiveness and value for money.
While there were no "quick fixes" and ministers were willing to consider new evidence and the experience of other countries, Mrs May said calls for a public debate on what could be done differently were "unnecessary".
There were "promising signs" that progress was being made and the "drugs landscape had been transformed", she added.
Mrs May said trends continued to be positive, with drug use in England and Wales at its lowest level since records began in 1996, record numbers completing treatment drug-free and drug-related deaths falling over the last three years.
The UK, she said, had taken the lead internationally in developing early warning systems to detect harmful new substances, with drugs able to be banned days after identification under the system of temporary class drug orders.
The government was working productively to "shift the focus" of treatment towards patients' long-term recovery and reintegration into society and a new payments-by-results approach to incentivise recovery outcomes was being piloted in eight areas.
Strategy was being co-ordinated across Whitehall, she added, while the proposed new National Crime Agency would, for the first time, "pull together the complete intelligence picture" and work with the police and other law enforcement agencies to co-ordinate a national response.