Other findings from the group's 2015 activity survey included that North Sea revenue fell to slightly over £24 billion last year - the lowest since 1998.
The group revealed that operating expenditure climbed by almost 8% and to record high of £18.50 per barrel of oil equivalent.
On the North Sea's future, the survey found that 6.3 billion boe-worth of projects were sanctioned or under development while less than 2 billion boe of the estimated 3.7 billion boe of potential investment opportunities were likely to be developed.
"Cost over-runs and project slippage on several large projects pushed capital investment in 2014 beyond expectations to £14.8 billion, with half spent on just 12 fields," the industry group said.
"As these large projects move from the investment phase into production there is very little new investment lined up to replace them; indeed, it is expected to fall in 2015 by around one third to £9.5 -11.3 billion."
Oil & Gas UK CEO Malcolm Webb said this year's activity survey painted a bleak picture but also identified the region's potential.
"Without sustained investment in new and existing fields, critical infrastructure will disappear, taking with it important North Sea hubs, effectively sterilising areas of the basin and leaving oil and gas in the ground," he said.
Cost cutting was seen as essential for the North Sea to remain competitive.
"Even at $US110 per barrel, the ability of the industry to realise the full potential of the UK's oil and gas resource was hamstrung by escalating costs, an unsustainably heavy tax burden and inappropriate regulation," Webb said.
"At current oil prices, we now see the consequences only too clearly. The industry recognises that its cost base is unsustainable. Cost and efficiency improvements of up to 40% are required to give this basin a viable future. This adjustment is now underway but cost control alone is not the answer."
"The basin needs sustained, high investment - £94 billion alone to recover the 10 billion boe in known reserves. This is why a concerted effort on three fronts is needed - tax, regulation and cost - to make the basin more attractive to investors and ensure that significant sums of much-needed capital come to the UK."
