Cabonne, Oberon and Walcha councils are taking action to challenge the legality of the provisions used by the NSW government in its Cabonne, Orange and Blayney merger proposal.

Cabonne Council has kept open its options to lodge an appeal and seek an injunction to prevent the proclamation of a merger with Orange and Blayney councils should its legal challenge this week be unsuccessful.

At an extraordinary meeting on Monday, Cabonne councillors voted to lodge a notice of intention to appeal against any adverse judgment and seek an injunction preventing Local Government Minister Paul Toole recommending that a proclamation be made, pending consideration by the council of the results of the case.

In doing so, the council voted to spend up to $20,000 on the legal expenses involved in lodging an intention to appeal.

Councillors were told the full cost of proceeding with an appeal could be about $150,000.

General Manager Andrew Hopkins said it was unknown whether other councils involved in the case would participate in that process.

He said advice from Cabonne's lawyers indicated it could take eight to 10 months before an appeal could be heard in the NSW Court of Appeal.

Earlier in the meeting, the council voted to provide a further $30,000 for legal costs for this week's case.

This amount is in addition to the $20,000 council originally resolved to spend.

If the case goes the way of the bush councils some say the merger between Wellington and Dubbo may come into serious question.

The case was expected to end on Wednesday and a decision is not expected for some time.