A continuing shortage of some essential medicines is to be investigated by MPs, following complaints by pharmacists that vital supplies are being lost to exports.

The All-Party Pharmacy Group, which announced its inquiry on Monday, said shortages in the supply chain had been occurring for two years and there was no sign of improvement.

The group said the reasons for drug shortages were complex but it was concerned that past efforts to resolve the problem had failed. It is seeking written evidence by December 23, ahead of issuing a report in the new year.

Lloydspharmacy, a unit of Germany's Celesio, said earlier this month that a survey of 396 of its pharmacists around Britain found 80 percent were unable to dispense certain items because of shortages.

Low prices relative to other European countries have fuelled exports from the country, leaving many pharmacies scrabbling for supplies, it said.

The export trade has been encouraged by a weak pound, which means Britain is now a particularly cheap place for middlemen to buy medicines and sell them on at a profit in other European markets.

Such so-called parallel trade is legal under European Union law and has long been an irritation for drugmakers. In the past companies have complained about cheap parallel imports flooding into the country when British drug prices were relatively high.

The new alarm over drug shortages in Britain comes hard on the heels of action by U.S. president Barack Obama to tackle an escalating shortage of life-saving medicines in the United States, due to manufacturing and supply issues.

(Reporting by Ben Hirschler; Editing by Greg Mahlich)