The Canal and River Trust signed a 15-year agreement with the Government in 2012 to look after 2,000 miles of canals and rivers in the UK, plus reservoirs and infrastructure.
But Lichfield MP Michael Fabricant says ministers have yet to confirm whether a new deal will be struck from 2027 onwards – despite the grant being overdue for renewal.
The deal saw the Department for Environment Food and Rural Affairs (Defra) commit to a property endowment worth £460m and funding of £800m.
Mr Fabricant, who is chairman of the Waterways All Party Parliamentary Group, has secured a Commons debate on the issue next week.
He said: "Regardless of whether you are a boater or just like walking along canal towpaths and enjoying the wildlife, our canal system is the envy of the world.
"Nine million people live within a 10-15 minute walk from an inland waterway and 83 per cent of them agree that these waterways are important to their area.
"But funding for these waterways is under threat. The trust’s 15-year grant expires in March 2027 and the grant is overdue for renewal.
"I shall be asking ministers to confirm the future of our waterways and towpaths. We cannot allow them to fall into disrepair."
The trust, which runs sites across the West Midlands, was set up in 2012 to replace British Waterways. It is responsible for 2,000 miles of canals and rivers as well as infrastructure including 71 reservoirs and more than 2,700 listed buildings.
The Inland Waterways Association has launched a campaign, saying that a "continued level" of government support was "essential".
The debate is scheduled for November 22 at 9.30am.