Edinburgh-based Wood Mackenzie warned that improved exploration and production performance this year could be crucial in ensuring the longevity of the UK oil and gas industry.
It cautioned that the acquisition of smaller companies and risk aversion among lenders was weighing on exploration.
Lindsay Wexelstein, head of UK upstream research for Wood Mackenzie, said: "Last year capital investment reached the highest level in real terms since the mid-1970s. We anticipate £21.3 billion will be spent on capital investment across 2013 and 2014.
"However, spiralling costs did put pressure on project economics."
This she said led to some developments being put on hold, such as US group Chevron's planned £6bn Rosebank development, 80 miles west of Shetland, and Norwegian company Statoil's work on the giant Bressay field, also off the islands.
Wood Mackenzie's annual UK upstream oil and gas review showed that the investment boom experienced by the industry since 2011 continued in 2013 but was expected to drop off from 2015.
Only 79 million barrels of oil equivalent (mmboe) in recoverable reserves were discovered in 2013, which Wood Mackenzie said was "fuelling concerns" about the longer term outlook for the industry.
"Just 52 exploration and appraisal wells were spudded last year. This is largely due to stretched company and service sector resources, as well as difficulties some companies faced in raising finance to fund exploration activity," Ms Wexelstein said.
She added: "There is a limited pipeline of projects that companies are working on beyond 2015."
Production has also been muted. At the beginning of 2013 it was expected 21 new fields would be brought onstream but only 13 materialised. This equated to 438 mmboe.
The consultancy expects a similar outcome in 2014, with 14 new fields with 438 mmboe forecast to be brought onstream.
Ms Wexelstein said: "Due to poor exploration performance in recent years, capital investment is unlikely to be sustained at the current high levels beyond 2015."
Exploration has been hit by the plunging numbers of ambitious smaller players in the North Sea and lenders' caution since the credit crunch. Ms Wexelstein said that the number of small North Sea explorers had plunged from 25 in 2010 to just five in 2013, as they were snapped up by bigger players.
"We have seen smaller companies that were more active drillers acquired," Ms Wexelstein said, citing Korea National Oil Corporation's 2010 purchase of Dana Petroleum.
"Some lenders are more risk averse," she added.
Cost pressures on the industry are coming in part from scarcity in skilled staff and in equipment including rigs.
Ms Wexelstein added that fields were increasingly expensive to develop with many located in deep waters, such as those west of Shetland; had reserves of heavier oil, such as Marnier; or were higher temperature, high pressure fields, such as Jasmine in the central North Sea.
Ms Wexelstein said: "Potentially one of the most significant events to take place next year will be the Scottish independence referendum in September, the results of which could ultimately lead to a division of oil and gas assets between Scotland and the rest of the UK."
But she added that of far greater concern to the industry currently were rising costs.
More merger and acquisition activity is expected in the industry in the coming year. Ms Wexelstein said: "Although some uncertainty remains over the longevity of the sector, 2014 could prove to be a pivotal year for the UK's North Sea."