Some of Britain's waterways may have to close amid funding cuts which have led to 180 job losses, the organisation which runs the 2,200-mile network says.
Union unison said job losses should be a "last resort"
British Waterways blames the cuts on a £7m drop in its funding from Department of Environment Food and Rural Affairs.
Defra's cost-cutting follows a £200m overspend - which it blames partly on bird flu fears and new farm subsidies
A merger of regional branches based in Tamworth, Staffs, and Birmingham will account for a third of the job losses.
Approximately another 60 jobs are set to go from the organisation's central office workforce, with a similar number being cut from its other British Waterways units.
Robin Evans, chief executive of British Waterways, announcing the job cuts, said: "I am announcing these decisions... because they are essential if we are to maintain our rate of progress.
"I accept that this is difficult news but we cannot be complacent in our management of the waterways network.
"We must constantly adapt and change to the circumstances around us, remaining committed to our vision of an expanded, vibrant, largely self-sufficient network enjoyed by an ever-increasing numbers of visitors."
A Defra spokesman described British Waterways as a "success story" over the past seven years with more than 200 miles of canal and waterway restored aided by more than £524m of government cash.
He said: "The in-year (annual) cuts of around £7m must be seen against this backdrop."
He added: "While Defra wishes to do everything it can to support the vision of British Waterways' board, they are aware that Defra is now operating within a very tight fiscal regime."
A spokesman for Unison, which represents many of the agency's workers, said: "We will fight these job cuts with every means at our disposal and we have arranged an emergency meeting of stewards to draw up plans."
"Unison believes it's an absolute disgrace that 180 hard-working loyal members of staff at British Waterways face the prospect of losing their job due to incompetence at Defra," a spokesman told the BBC.
"Job cuts should be a last and not the first resort," he said.
The union, which has called for talks to consider alternative options before staff are made redundant, claimed it had been given "an assurance" in the summer that there would be no "knee-jerk reaction" to funding cuts.