NSW Nationals Senator John Williams says he will cross the floor to support a royal commission into the banks but believes his lower house colleagues will be discouraged from doing the same, especially if the government agrees to establish a new tribunal to hear customer complaints into so-called “bank bastardry”.

With Labor intending to move motions in both houses of Parliament in an attempt to embarrass the government into calling a royal commission,, Senator Williams, who has worked hard over the years to help expose bank scandals, said “if it comes up, I’ll vote for it”.

But with Labor, the Greens and most of the Senate crossbench already prepared to support a royal commission, the numbers easily exist in the Senate and Senator William’s vote will not be pivotal.

Of greater concern to Prime Minister Malcolm Turnbull will be his threadbare majority in the lower house where just one defection could see his government suffer an embarrassing loss.

Labor leader Bill Shorten is goading Coalition MPs who feel strongly on the issue to cross the floor, claiming they must make a choice between the banks and “the Australian people”.

The government’s slender majority has become even more precarious after Labor adopted a tactic used by Tony Abbott against the Labor minority government when he refused to grant pairs.

Typically under a pair arrangement, a Labor MP would abstain from voting in the House of Representatives if a Coalition MP was absent due to illness or some other reason.

Labor’s manager of Opposition business, Tony Burke, said pairs would be rejected which would test the Coalition’s one-seat majority whenever an MP is absent.

Senator Williams said while he did not believe anyone would cross the floor in the lower house for a royal commission, given the greater consequences of destabilising the government, they could be discouraged from doing so with the formation of the tribunal.

“The tribunal will take the steam out of it,” he said.

Binding rulings

The tribunal, which is being pushed hard by Queensland Liberal Warren Entsch, was recommended in May by a Senate inquiry, led by South Australian Liberal David Fawcett. Essentially, it would enable people to test grievances against a bank without having to pay, unlike if they had to go to court.