Over 200 HS2 employees have left the state-funded rail group over the past year, as it looks to improve stability and tackle the level of churn.
Some 170 employees have resigned since 1 November last year up until 31 October this year, while 77 employees were made redundant within the same period.
The figures come from rail minister Paul Maynard in response to a written question from Cheryl Gillan, Conservative MP for Chesham and Amersham.
HS2 declined to comment last night on the figures provided by the rail minister. However, HS2 boss Mark Thurston, who is the group's third chief executive in six months, addressed the topic of staff turnover in front of the Public Accounts Committee last week.
He told MPs that staff turnover at HS2 was 18 per cent, acknowledging it as "far too high", but said the trend is now improving.
Among the reasons flagged for the fluctuation were the move of HS2 headquarters from London to Birmingham, and the shift in what the group's purpose is, as it moves onto the next stage of the project, from planning into delivery.
However, HS2's boss has also noted the need to work harder at retaining talent.
"I've spent the lion's share of my first eight months in this job reinforcing the need for stability, for good corporate discipline, clarity around what the purpose of the organisation is, because it has changed quite a lot," Thurston added.
There are around 1,500 people employed at HS2 currently, and around 280 have been there more than three years.
The £56bn rail project will span London, Birmingham, Manchester and Leeds, with the government saying the new railway line will bring "huge economic benefits across the country".
But the rail group has weathered a turbulent period of late, after a National Audit Office report in July found HS2 had proceeded with £1.76m of unapproved redundancy payments, despite them being forbidden by the Department for Transport.
At the end of last month, HS2's chief financial officer Steve Allen stepped down over the matter, saying weaknesses highlighted in the NAO report resulted in both the HS2 executive and board being "misinformed about the status of critical approvals for redundancies".
"Those assurances were given by teams for which I was responsible and, obviously, I regret that," he added.
Allen and Thurston then faced a grilling by MPs on the PAC last week over the redundancy payouts. There it emerged that HS2's former chief executive Simon Kirby, now chief operating officer at Rolls-Royce, had received an email from a senior figure at the DfT instructing that redundancy payments should not top £95,000 per person, and had not forwarded it onto colleagues.
Kirby said in a statement afterwards that he did not approve the payments at issue, and denied any allegation of wrongdoing.