The competitiveness of UK businesses will suffer unless key road, rail and other infrastructure projects are built, said a new report.
Research from the CBI business lobby group added that confidence among British firms that the delivery of key building projects will improve in the next five years has fallen over the past 12 months.
Its latest CBI/AECOM infrastructure survey said confidence levels among firms had fallen to 27% from 43% a year ago.
Carolyn Fairbairn, CBI director general, said: "Announcements and commitments are one thing. Seeing tarmac, tracks, and super-fast internet cables being laid is another.
"If we don't get spades in the ground on existing plans, it's clear we could put a major dent in the competitiveness of British business – and the UK itself. This is something we cannot afford to do, especially during this period of uncertainty as the UK leaves the EU."
The report comes amid the government's backing of a £16.5bn ($20.6bn) third runway at Heathrow last month. Although critics point out that the long-delayed project still faces a parliamentary vote next year, a planning inquiry and a likely judicial review before the runway is operational by 2026 at the earliest.
In September Prime Minister's Theresa May's new government also gave the go-ahead to build the £18bn Hinkley C nuclear power station, with the aid of the Chinese and French. This project is expected to take nine years to complete.
Autumn Statement infrastructure boost
Later this month as part of the Autumn Statement chancellor Philip Hammond is expected to speed up the UK's infrastructure building in a bid boost the economy following a slowdown of business investment after the country's June Brexit vote.
However, the CBI research found that almost half of the firms it surveyed were dissatisfied with their own regional infrastructure, including broadband provision and the state of road, air and rail links.
A Department for Transport spokesman said: "We are delivering a record £70bn investment in rail, roads, ports and airports.
"Within this, we are funding the biggest rail modernisation programme since Victorian times and the most extensive improvements to roads since the 1970s.
"Work is due to get under way on HS2, and Crossrail is set to open in 2018.
"We also gave the go-ahead for Heathrow, which will bring benefits to passengers and the wider economy worth up to £61bn."