The Bexhill to Hastings Link Road will not be opening in May next year, it has been confirmed this week.
East Sussex County Council has blamed a wet winter and sodden late summer, and the £113m road will now not open until later in 2015.
But the county council has refused to set a new date.
Extensive archaeology work carried out on the site also added to the delay, which was revealed at a Link Road information event in Sidley last week.
And ESCC told the Observer that further progress on the project is dependant on the weather over the forthcoming winter months.
The Combe Haven Defenders are calling for the council to be more transparent over the delay.
The group has been a vocal opponent to the BHLR, with members taking to the treetops during protests when the work commenced early last year.
Anthony Bradnum, of the Combe Haven Defenders, said: “For almost two years, East Sussex County Council has been telling us that the link road would open in May 2015.
“Now it appears that will not be the case, but ESCC has not seen fit to share that information publicly.
“An extended construction time is likely to lead to increased costs, and we feel that the county council should be open and upfront about the implications of this entirely predictable delay.
“They are already wasting £113m of public money on this disastrous project and if the cost is to increase even further, we have a right to be told.”
But an ESCC spokesperson said that the £113m Link Road budget included a contingency fund to meet extra costs incurred by unforeseen issues, such as bad weather.
She told the Observer: “Work is progressing with the construction of the Bexhill to Hastings Link Road but, as with every major road scheme, the actual opening date is subject to a range of factors such as exceptional weather, the extent of archaeological discovery and investigation, and seasonally restricted environmental work.
“We endured record levels of rainfall in the months of December 2013, January, February, August and October 2014 which on occasion saw three times the average rainfall for the area.
“Despite taking actions to mitigate the effects of this extreme weather, through alterations to the programme of work, there has been an impact on some of the key activities on site.
“Similarly, the progress of work on a number of the remaining weather sensitive activities will also depend upon the type of winter we experience.
“In addition the archaeologists have made a larger than expected number of significant discoveries and it is important that the experts were given time to analyse those findings and their potential impact on other areas of the site.
“We are hoping for a mild winter which will allow us to get back on track in early spring and minimise delays.
“There is a contingency built into the budget for the Link Road which covers delays caused by winter weather.
“The road will help bring 2,000 new homes, 3,000 new jobs and more than £1 billion of economic benefits to the area. It will also relieve the traffic congestion on the A259 between the two towns.”