The draft budget threatens the very foundations of economic growth, leaving Northern Ireland the "poor relative" in the UK, it's been claimed.
The Construction Employers Federation said the 2015/16 budget would result in investment in public buildings and infrastructure from schools to roads falling by over 20% in real terms next year.
Managing director John Armstrong said: "It is recognised the world over that high quality infrastructure is the starting block for sustainable economic growth.
"In infrastructure terms, Northern Ireland is the poor relative across these islands. Cutting investment will only put us further behind, particularly at a time when the British government continues to boost infrastructure spending."
The draft 2015/16 budget will see over £870m cut from certain public services in Northern Ireland, with around £710m reallocated to meet other spending pressures.
Mr Armstrong said the Executive had been sacrificing investment in the "foundations for economic growth" as it coped with pressures on resource expenditure.
But proposals in the draft budget went too far, he said.
"The current plan to divert capital funding away from delivering infrastructure in order to pay off the £100m short term treasury loan and the £100m redundancy scheme is a step too far."
He said the conventional gross capital investment budgeted for in 2015/16 was 45% lower than that of 2009/10.
"The percentage fall in non-ringfenced resource expenditure over that same period has been much less.
"For Northern Ireland to prosper, additional funding for capital investment must be found."
He said the plan for a Northern Ireland Investment Fund would not deliver anything until late 2016 at the earliest.