A backflip by Liberal leaders to cut billions in regional telecommunications safeguards has triggered a boycott by shadow communications minister Nick Minchin and almost half the voting members of the Coalition.

Coalition backbenchers joined Minchin, a long time rival of party leader Malcom Turnbull, and crossed-the-floor and walked out of one of the final senate meetings this year as the party relinquished its election promise to safeguard the $2.4 billion Communications Fund and instead pour it into the government's $26 billion Infrastructure Australia initiative.

Legislation drafted by the then Howard government to protect the fund was bypassed by a senate majority to appropriate the cash to stimulate investment in the economy. The backflip decision occurred after the party had voted to preserve the fund in the lower house and first senate round.

Attempts by the government to use the fund for its $4.7 billion National Broadband Network (NBN) were previously vetoed by the legislation which passed late last year . The bill was designed to restrict the now Labor government to spending only the interest earned from the Communication Fund's investments — up to $400 million every three years.

A spokesperson for Minchin's office said the funds may be used to fund the government's NBN.

“Who knows what will happen to these funds that were an important revenue for regional Australian telecommunications,” the spokesperson said.

“They could end up funding the disaster that is the NBN.”

Less than two weeks ago, Nationals leader Warren Truss said he expected the opposition to push amendments to protect the Communications Fund.

“[The Communications Fund] is likely to go to failing Labor states and territories to fund infrastructure projects that in some cases were originally promised last century. Meanwhile, rural and regional people will suffer, as they have done right through Rudd Labor’s first year in power,” Truss said.

Nationals Queensland senator Ron Boswell was one of four party members to cross the floor, along with two Liberals and a raft of abstaining members. Only five Liberals voted for the move.

Boswell said in a written statement the move was a deal-breaker with the bush.

“Those who ignore the interests of the bush will pay a political price,” Boswell said

“There is an important lesson to be learned from last night and that is to never, ever ignore rural Australia. Their voice will be heard in our parliaments."

Independent senator Nick Xenophon and Family First senator Steve Fielding voted against the move.

Minchin labelled the change a “Mickey Mouse” vote.

National Party leader Barnaby Joyce told ABC News Radio the move destroyed taxpayer trust established during the sale of Telstra from which the fund was created. “I am disappointed that the telecommunications fund that we bargained for was removed; it was there to protect regional telecommunications,” Joyce said

“The Labor party flushed it down the toilet and promised [the NBN] which leaves out regional Australia.

“A vast number of people obtained from the vote because you cannot take the Australian people on trust that you will protect the Communications Fund. That is one of the reasons why [the public] allowed the sale of Telstra, and they have reneged on that trust.”