Patients are suffering because of a shortage of some NHS prescription medicines, a Parliamentary group has warned.
Shortages of some medicines are having an "adverse" impact on patients such as diabetics, epilepsy sufferers, pregnant women and those with mental health problems, Parliament's All-Party Pharmacy Group said.
In a report detailing its inquiry into medicine shortages, the group said the shortages had been mainly caused by the export of medicines intended for the UK market to other EU countries.
"Evidence we received highlights the stress, anxiety and sometimes harm that patients suffer," the MPs said in their report.
"We have no objection to the export of medicines in principle, so long as this practice does not harm patients," they said.
The shorter reserves of medicine are causing pharmacists to spend an increasingly large amount of time trying to track down the right medicine, the MPs noted.
But in spite of the best efforts of pharmacists, the group said it had been told of cases involving vulnerable patients not receiving the medicine they need because of shortages.
Katherine Murphy, chief executive of the Patients Association, said: "The very least patients should be able to expect is for prescribed medicines to be available to them when required.
"However, all too often this simple expectation is not being met and as a result patients, some of whom have serious medical conditions that require medicine to remain stable, are being put at risk."
Rob Darracott, chief executive of Pharmacy Voice, which represents community pharmacy owners, said: "Pharmacists up and down the country are making extraordinary efforts to get medicines to their patients promptly, and in most cases succeeding.
"But there is a long-standing problem with medicines delays which must not be allowed to continue indefinitely.
"The Government needs to investigate this problem as a matter of urgency, using the findings of this report as a starting point."