Discoveries of new oil and gas reserves dropped to their lowest level in at least two decades in 2014, signalling tighter world supplies as energy demand increases in the future.

Preliminary figures suggest that the volume of oil and gas found last year, excluding shale and other reserves onshore in North America, was the lowest since at least 1995 (based on previously unpublished data from research company IHS).

New finds of oil and gas are likely to have been about 16 billion barrels of oil equivalent (boe) in 2014, making it the fourth consecutive year of falling volumes.

That is the longest sustained decline since 1950. As new oilfields generally take many years to develop, recent discoveries make no immediate difference to the crude market, but they give an indication of supply potential in the 2020s.

Peter Jackson of IHS said: “The number of discoveries and the size of the discoveries has been declining at quite an alarming rate. If you look at supply in 2020-25, it might make the outlook more challenging.”

So far, there has not been a single new giant field — one with reserves of more than 500 million boe — reported to have been found last year.

The figures for declining discoveries are particularly striking, because exploration activity in 2014 showed little impact from the sharp fall in oil prices in the second half of the year. The last time oil and gas discoveries were around 2014’s level was in the mid-1990s, when exploration activity was hit by a period of weak prices.

There are also very large shale oil reserves in countries including Russia, China, Argentina and Libya, but the industries there are still in their infancy. Shale is also a relatively high-cost source of oil compared with reserves in the Middle East, so it requires higher crude prices to be commercially viable.

Mr Jackson said that with crude prices around their present levels, it would be “very difficult” to start up new shale production projects.