MPs are unlikely to hold their first debate on legislation authorising HS2 for another two months because of problems with the consultation process.
A parliamentary committee ruled the omission of 877 pages from an Environmental Statement on HS2 as well as other errors meant the closing date for consultation should be extended.
The body building the rail link said it was happy to comply with the timetable.
But critics said the errors proved those in charge were "incompetent".
A public consultation on the environmental repercussions of Phase One of the £50bn project - which will build a high-speed line between London and Birmingham - was due to end on 24 January.
But campaigners called for it to be extended after the pages of key documents were initially left off a computer memory stick that was submitted in evidence as part of a 50,000 page report.
The 17-day extension was granted following a rare meeting of the Commons Standing Orders Committee, which last sat in 2008.
BBC parliamentary correspondent Mark D'Arcy said this meant the first general debate on the government's HS2 bill - which is backed by the three main parties but opposed by some MPs - was likely to be delayed to 27 March at the earliest.
The Stop HS2 campaign group said it showed "those in charge of HS2 have been proved to be completely incompetent".
"A few typos would be excusable, but missing hundreds of pages is gross incompetence," its spokesman Joe Rukin said.
The current consultation was the shortest to date, he added, and did not leave enough time to give a "reasoned response".
But a spokesman for HS2 Ltd, the firm developing and promoting the project, said the committee had confirmed the bill "can proceed as planned".
"We are happy to comply with the committee's instruction to extend the Environmental Statement consultation period for a couple of weeks, to allow for full and proper consultation on some pages that were missing from the original material," he said.
"HS2 is the most significant infrastructure project the UK has seen in modern times and a project the country cannot do without."