So far the authority has committed £150,000 towards the campaign, of which £130,000 has been spent.
Now councillors are to be asked to add another £100,000 to the pot.
If approved, much of the money is to be spent on lobbying in relation to the HS2 hybrid bill that is due to go before Parliament.
When the council last pledged money towards the anti-HS2 battle - £50,000 in August 2012 - there was criticism from some that it was a waste of taxpayers’ money, particularly given the economic climate.
Council leader John Cartwright said the authority needs to do all it can not only to try and stop HS2 but also to ensure the best deal for the area if it goes ahead.
Mr Cartwright said: “I hope and believe we will not spend that amount of money, but we need to have it available.
“We need to be in a position to authorise a payment almost at a moment’s notice, rather than have to go through the procedure of calling all of the council in.
“HS2 is unique. It’s not a question of saying ‘we’re a bit short this time, we won’t put any money in now but we’ll do it next year’.
“The opportunity only comes around once to be able to oppose parts of it.
“HS2 is going to destroy Buckinghamshire and I feel we have a duty as a council to do everything that is humanly possible to oppose it.”
The proposal to pledge another £100,000 is due to go before the council’s cabinet on Tuesday (June 11).
If approved it will need to be passed by full council at a later date.
At a recent meeting of Wendover Parish Council, members were split over whether more money should be put towards fighting HS2 in the courts.
The council committed another £5,000 to the fight, but Councillor Bob Lewis said it was ‘futile’ to do so.
He said: “I think it’s preposterous that council tax payers’ money should be spent in this way.”
His comments were supported by Councillor Stephen Worth, who said: “The Wendover residents who talk to me are against spending any more money on fighting HS2.”
Mr Lewis said it would be better to put money towards lobbying the hybrid bill, but Councillor Marion Clayton said it would be too late by then.
Ms Clayton said: “We have to try and stop it before it gets to that stage.”