Better safeguards are needed to protect areas of ancient woodland along the HS2 track, according to a report by MPs.
The report also warns that the high-speed trains must run slower than the planned 225mph to cut carbon emissions and ensure the £50bn scheme is built without excessive damage to the environment.
The report by the Environmental Audit Select Committee found that plans to minimise any damage do not go far enough and called for better safeguards, including a separate ring-fenced budget for environmental protection.
The committee said not enough is being done to protect areas of countryside which should not be subjected to "crude calculations of cost and benefit."
The Woodland Trust announced before Christmas that long-established woodland would be trashed by HS2, including New Years Green Covert on the edge of Ickenham.
In a report released on December 19, the Trust said the damage HS2 would do to New Years Green - one of 67 ancient or other woodlands at risk - would be severe .
The Government report comes just a few weeks before the hybrid bill, allowing construction to begin on phase one of HS2 from London to Birmingham, will receive its second reading in Parliament.
In December, HS2 Ltd revealed in its full environmental impact statement in the Hybrid Bill that all breeding populations of Barn owls within one-and-a-half kilometres of the track will be wiped out .
