HS2 Action Alliance (HS2AA) is seeking two judicial reviews of the scheme, whose first phase will see 200mph trains running through Tory heartlands between London and Birmingham.
The group said one of the reviews it was seeking dealt with environmental issues and the other was about “fighting for a fair deal for compensation”.
HS2AA, which works with more than 70 local groups opposed to HS2, said that in dealing with the environment and compensation the Government failed to follow the proper processes.
HS2AA said that if proper processes had been followed, the Government would have reached a different conclusion about HS2, whose second phase will see a Y-shaped route going north to Leeds and Manchester with links further north to Scotland.
HS2AA said yesterday it had had “a brilliant response” to its appeals for funds for taking legal action.
It said the Government had 21 days from tomorrow to respond, with a judge being allocated to decide if there is a case to answer.
A Department for Transport spokesperson said: “We believe we have struck the right balance between the reasonable concerns of people living on or near the line (who will be offered a package of compensation measures), the environment and the need to keep Britain moving.
“We will be vigorously defending any legal challenge.”