The High Speed Rail 2 Action Alliance (HS2AA) is bringing two judicial review claims against the Department for Transport (DfT), tackling environmental issues and the compensation which will be paid to affected residents.
"In both cases the Government failed to follow the proper processes required – if they had they would have reached a different conclusion," the group said in a statement.
Its announcement follows the launch of a further judicial review of the Government's decision to go forward with the £33 billion project, brought by the '51m' alliance of 18 local councils affected by the plans. 51m has claimed the plans are "fundamentally flawed and poor value for money", and that the Government did not adequately consult on changes to the route which were first announced on 10 January.
The Government has 21 days to respond from the date it is served with the claims.
HS2AA claims that the public were prevented from giving a meaningful response to the Government's proposals for compensation for property owners suffering from 'generalised blight'. The Government's 2011 consultation on HS2 did not provide adequate information, it said, meaning that the decision on compensation was taken "without proper justification, [ignoring] their own criteria and [relying] on new undisclosed material". It added that the decision "did not meet the expectations that had been created by Government", which had promised a "fair deal" for those affected by the work.
The Government also did not carry out a full strategic environmental assessment (SEA) of the HS2 route, HS2AA said. Under the SEA Regulations, an assessment must be carried out for any important infrastructure project before proposals are presented for public consultation. Environmental group Berks, Bucks and Oxon Wildlife Trust (BBOWT) has written to the European Commission separately on this issue, it said.
"The Secretary of State's decisions on high speed rail remain as set out in January and work on HS2 is continuing as planned," a DfT spokesperson said. "We are confident that the process by which she reached those decisions was lawful, appropriate and fair, and we will be vigorously defending any legal challenge."
The spokesperson added that the proposed route between London and Birmingham had been "continually improved" to mitigate its impact on local residents and the environment.
"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," the spokesperson said.
Network Rail has predicted that the UK's current main rail link, the West Coast Main Line, will be operating at full capacity by the mid-2020s.
The initial London to Birmingham phase of the 250 miles per hour line, which is scheduled for completion in 2026, will cut journey times between the two cities to 45 minutes. The proposed second phase of the project envisages the construction of an onward 'y network' connecting the line to Manchester and Leeds, as well as a spur to Heathrow Airport, by 2033. A formal consultation on the route for this second phase will begin in early 2014, the Government has said.
Legislation that will enable construction on the project to begin is due to be introduced at the end of next year. However Patrick Twist of Pinsent Masons, the law firm behind Out-Law.com, urged the Government in January to commence building work "at the earliest opportunity".
"HS2 will create a step change in capacity and connectivity between England's largest cities," he said. "It will enable the economy to grow, creating jobs and spreading prosperity more evenly through the country. The new railway now needs to be advanced with a firm commitment that builds on the impetus of [the Government's announcement]."