A £100,000 appeal will be supported by Aylesbury Vale District Council if a High Court legal challenge over HS2 is rejected.
The council will find out in the new year if a judge agrees with it that the Government acted unlawfully when it approved the high speed line.
If not, an appeal would need to be lodged within seven days and cabinet members have agreed to back the move.
The council has previously pledged £150,000 to the legal challenge which covers its contribution to the appeal.
The authority is part of a coalition of 15 councils which are prepared to spend £1.3 million fighting HS2.
Another member of the group, Bucks County Council, has pledged £500,000 over three years.
Councillor John Cartwright, district council leader, said: “Those residents and businesses in Aylesbury Vale that will be affected by the planned route have put their faith in this authority to help them in their fight against it.
“Whatever the outcome of the judicial review issue, we will still maintain an objection to key aspects of the project and will continue to seek to persuade others that it should not go ahead.
“This scheme will have a seriously detrimental effect on the Vale, which could last for decades.”
So far £165,000 has been spent bringing a judicial review, which equates to 9p for every resident in the 15 council areas.
The estimated £100,000 cost of appealing is likely to be met by the 51m coalition rather than one council on its own.