A large number of people who have engaged with a National Party questionnaire about what it wants from its elected members at the next federal election have urged their MPs to fight against council amalgamations.

Two sources who received a questionnaire via email or post about issues affecting their electorate were surprised by the amount of people passionate about the mergers in their region.

One source told Fairfax Media "there have been many people who have told the party amalgamated councils are a big issue and they want their federal MPs to support them by opposing the mergers."

"The Nationals leader and Deputy Prime Minister Barnaby Joyce has already told the Premier of NSW he opposes Walcha being merged. It's beginning to be a toxic issue for the Nationals," the source said.

The list of National MPs opposing merger is growing. Dr Peter Hendy, the member for the bellwether seat of Eden Monaro, which has gone to the party that has formed government in every election since 1972, said he was opposed. Swinging voters could cost Dr Hendy his seat.

"I have written to the NSW Premier outlining my opposition to the forced council merger between Palerang and Queanbeyan councils. I have always maintained that community support, and a strong business case are vital," Dr Hendy said.

Dr Hendy, The Nationals state MP for Tamworth Kevin Anderson, Liberal federal MP for North Sydney Trent Zimmerman (standing in former treasurer Joe Hockey's seat) who admitted he had lost votes because of mergers in his electorate, together with state members for Barwon Kevin Humphries and Orange Andrew Gee have all expressed dissatisfaction with forced amalgamations.

In Western NSW the seats of Calare and Parkes are held by big margins but backed by the Save Our Councils Coalition, a lobby group who are working with big city and country councils and anti-amalgamation groups, is asking the federal members to sign a pledge to oppose the mergers.

"The letter to all Liberal and National MP's is being sent out now [Friday]. We are a small group but wielding a big stick because we have the growing backing of community support who say they will put the fear of God into the MPs who support mergers. Many of these people have voted for the Nationals and Liberals all their lives, some multi-generational."

They are backed by heavyweight broadcaster Alan Jones, who has warned the NSW Premier to rethink the issue. He told the Liberal Party to "wake up to itself".

The state member for Orange Andrew Gee, who is now the federal candidate for Calare, has been a vocal campaigner for Cabonne and attended several meetings in the LGA to oppose it.

The federal MP for Parkes Mark Coulton, who was on a marathon journey to Broken Hill to meet community members in a new sector of his expanded and bulging electorate, said when he was mayor of Gwydir between 2004 and 2007 he had been through the merger process.

"It is really a state government issue. I understand the anxiety and emotion but until I hear the evidence and the findings of the NSW Boundaries Commission I can't be clear on it. I am happy the process is proceeding though."

Cabonne and Oberon councils have joined others and are heading to the NSW Land and Environment court on May 24 and 25 determined to win.

There are no signs the state government will back down to minimise the electoral damage and now the federal election is being seen by some as a litmus test for communities in which mergers are opposed.

The Save Our Councils Coalition are watching the by-election for the state seat of Orange, which will be held after the federal election.