The first phase of the £55 billion project connecting London to Birmingham is scheduled to be completed by the end of 2026, while its extension to Crewe through Staffordshire will be finished a year later.
But Stop HS2 campaigners have declared that deadline will be missed because construction on stations in Birmingham and London has been pushed back.
The objectors state it was originally planned for building work to start in 2018 but now it has been revealed that tendering out the contracts to firms looking to deliver the stations will not start until that year, and announcements on the preferred bidders will not be made until 2019.
The group has declared it is now 'clear' the first phase of HS2 will not be open in time. Campaigner Joe Rukin said: "HS2 Ltd have released a timetable which says they will only start tendering for station construction when they previously thought there would be spades in the ground.
"It is clear that if the Birmingham and London stations are going to be a year or two later than previously thought, then the proposed opening of HS2 for Boxing Day 2026 is no longer on the cards.
"It is no surprise that HS2 Ltd have failed to hit their timetable, as with breath-taking incompetence as standard, they have missed every single deadline so far."
But HS2 Ltd have completely refuted the claims and declared the project is still on schedule with Phase 1 opening as planned and Phase 2, providing links to Leeds and Manchester, to be completed by 2033.
HS2 spokesman, Ben Ruse said: "There is no change to the planned operational date for HS2. HS2 constantly reviews its design and construction procedures against best practice in the UK and around the world.
"We are now able to start construction on parts of this vital national project later, reducing periods of disruption while maintaining the completion schedule."
At the moment the legislation for Phase 1 is making its way through the House of Lords and HS2 Ltd expect to have Royal Ascent by the end of the year.