An exclusive survey for Sky News shows that three quarters of businesses are considering dropping the Royal Mail as a national strike looms.
The poll in conjunction with the British Chambers of Commerce for Jeff Randall Live also found that almost nine out of 10 companies are concerned about a postal strike.
At the same time, 93% of businesses think that recent disruption to the postal service has damaged the Royal Mail's reputation.
Speaking to Sky's Jeff Randall, Steve Hughes, economic policy adviser to the British Chambers of Commerce, said the survey highlights the fears raised by the threat of a walkout.
"The results of this survey are quite explicit, they are very upset by what's happening and they're worried about how it will affect their services," he said.
"In terms of who they blame, I think all they want is consistency within the service. That means the Royal Mail providing a service that they can rely on. At the moment they can't do that."
The comments came just hours after the Communications Workers Union announced that their members at the Royal Mail had voted in favour of the first national postal strike in two years.
At the same time both the Confederation of British Industry and the Institute of Directors warned that a walkout would cause even more problems for recession-hit businesses.
John Cridland, deputy director general of the CBI, said: "After a very tough year, serious disruption to the postal service would present a real threat to those firms pinning their hopes on a pre-Christmas sales bounce.
"We need common sense to prevail and lasting damage to be avoided."
Meanwhile, Graeme Leach, chief economist at the IoD, said: "A national postal strike now will be very damaging to business.
"Postal workers need to understand they are shooting themselves in the foot."
Institute of Dictators 
OMG They are cloning them 
