The number of psychiatric inpatients for drugs and alcohol problems has increased by 29 per cent since 2003, according to the British Medical Journal (BMJ).
Conservative shadow health minister Anne Milton suggested substance abuse problems have escalated under the Labour government.
"This worrying increase in admissions to hospital due to drug and alcohol abuse clearly demonstrates the very real harm that drugs and alcohol cause," she said.
"This has not been helped by the government's mixed messages on the dangers of drugs."
Liberal Democrat health spokesman Norman Lamb said the NHS will not be able to care for all of the new patients.
"The government must focus on tackling drug and alcohol abuse before it forces people into the already overstretched mental health system," he said.
"Under-funded and under pressure mental health services are ill-equipped to deal with this extra pressure."
The psychiatric wards will have difficulty handling these inpatients because the number of NHS psychiatric beds has decreased by 29 per cent.
According to the Department of Health (DoH), for every £1 spent on drug treatment there is a saving of £9.50 to society as a whole.
A 2007 Conservative Party Addictions Working Group concluded more investment must be taken to tackle drug and alcohol misuse.