Chambers of commerce from across the country have written to the Prime Minister demanding that he approve expansion of Heathrow airport by the end of year.
They warned that any delay raised "grave concerns" about the future credibility of the new National Infrastructure Commission and cast doubt about whether it would have real power to make big decisions.
The letter says: "Heathrow expansion will increase our area's connectivity, add more long-haul connections, and help us to boost exports, investment and tourism.
"Given how long it has taken to get to this stage, and to the Airports Commission's final recommendations, we are deeply concerned at the prospect of any further delays.
"Our businesses tell us that ministers' statements on growth and exports mean little if the government cannot take the tough decisions needed on key infrastructure projects.
"Our businesses want delivery, not more reports and recommendations. We want to see Heathrow expansion approved by the end of the year, as promised."
The letter was signed by more than 20 chambers of commerce from across the country, including Glasgow, Liverpool, Cornwall, the North East, Northern Ireland and Leeds.
There is speculation that the Government is set to announce a delay in making a final decision on airport expansion in the South East.