Campaigners opposing plans for a new eco-town at Weston Otmoor are planning to take their case to the High Court.
The Weston Front, formed to fight the controversial 15,000 home development, will join forces with fellow anti eco-town protesters, campaigning against a similar development at Middle Quinton near Stratford upon Avon to take the Government to judicial review.
The Weston Front is backed by former tennis British number one Tim Henman's father Tony, who lives in nearby Weston-on-the Green.
He said: "The arguments being put forward to all practical purposes are virtually identical to our case, although we have some additional complaints.
"We have not been told the criteria under which we have been selected as a potential site for an eco-town and we believe the consultation process has been fatally flawed."
The Better Accessible Responsible Development Campaign, which opposes the Middle Quinton scheme is expecting to go before a High Court judge in the next month to determine if there is sufficient evidence for the case to go ahead.
If there is, the Weston Front will join in the legal action as an "interested party" in a bid to get the Government to rethink their plans on eco-towns.
A list of 27 potential sites for eco-towns was originally released by the Government, with a shortlist of 15, including the Weston Otmoor site, announced in April.
The Weston Front claimed the site, which included part of the greenbelt, was inappropriate - and that they had not been told why, or how it was chosen.
Mr Henman said: "We are hoping this will force the Government to either withdraw from the whole process on the basis that it is fatally flawed or they will have to start all over again.
"We are all in agreement that we need more housing and more affordable housing but there are different methods of increasing the housing numbers."
He said houses should be built in Oxfordshire's existing towns, such as Didcot, Banbury, Bicester, Wantage and Witney, rather than on a new site.
Oxfordshire county and Cherwell district councils both oppose the scheme.
Mr Henman said if the action went forward, the Weston Front would apply for their financial costs to be protected, meaning if they were unsuccessful they would not be hit by a huge legal bill for the Government's court costs. It is expected their own legal costs will be in the region of £1,000.