When Tim Storer finally spoke, he spoke clearly. But it was not what the government wanted to hear.

He would not support the Turnbull government’s “narrowly cast proposition of change” because after widespread consultations, including with business, he remained unconvinced by the arguments for reducing the corporate tax rate for Australia’s biggest companies.

“After undertaking that process, I remain to be convinced that, in isolation from a broader discussion and initiatives on enhancing the overall sustainability of our taxation system, that I should support this bill in its current form,” he told the upper house on Wednesday.

Senator Storer, 48, confounded Canberra journalists by laying low over the past week instead of bathing in the glow of national media coverage.

Instead, the newly minted senator’s parliamentary door was often locked to keep out the press gallery’s most enterprising journalists.

By the time he finally broke his silence on Wednesday, Finance Minister Mathias Cormann had already given the game away, revealing the night before that the government had not won the South Australian’s vote.

In the Senate, Senator Storer told the government its stated aim of slashing the corporate rate five cents in the dollar to 25 per cent for big business was probably not “prudent … in the face of Australia’s budget deficit and debt”.

The South Australian was a failed Nick Xenophon Team candidate for the Senate in the 2016 election. He resigned from the party before being appointed to the Upper House to replace Skye Kakoschke-Moore in February 2018 after she fell victim to the dual citizenship fracas.

Senator Storer, who has an economics degree, an MBA and extensive experience as a business consultant, suggested the effect of the government’s tax plan would be “modest relative to its cost”.

There were better ways to spend the $35.6 billion in revenue, including “well-targeted social and economic programmes”, such as “funding of world-class education and health systems” and “reducing inequality”.

And rather than calling for specific concessions, as Pauline Hanson had with a $60 million apprenticeships trial or Derryn Hinch had by requesting political cover in the form of more money for pensioners, Senator Storer engaged with the legislation at hand.

He noted the Rudd government-commissioned Henry Tax review had suggested a drop in company tax as “only one of a number of principal feature reforms which have not been acted upon”.

The government’s reforms, by comparison, were piecemeal, he argued.

Senator Storer stressed that his contribution on Wednesday was not his maiden speech. Nevertheless, Senator Cormann strode across the almost-empty chamber to shake his hand when he had concluded.

Before entering Parliament, Senator Storer worked as a business consultant who specialised in helping South Australian companies interact with China, and he served on the Australia China Business Council.

He was the new senator the government had been hoping for, the assumption went.

That was on top of new senators Fraser Anning and Steve Martin, also beneficiaries of the citizenship crisis, who backed the tax cuts.

Instead, Senator Storer confounded once again.

When he asked his first question in Question Time on Wednesday afternoon, he invoked the Business Council of Australia (BCA), the chief lobbyist for the government’s corporate tax plan.

But the issue was far away from tax cuts – he called for an increase to Newstart to “meet the current need”, a case the BCA has also made.

Senator Hinch also said he would not be backing the tax cuts on Wednesday.

“I have had – and am still having – cordial conversations with Finance Minister Cormann,” he said in a statement.

“At this time, I remain unconvinced. I said, when this session of Parliament started, that I would not negotiate in the media. I don’t intend to start now.”

Still, the Victorian appeared more eager to wheel and deal.

Senator Storer’s two-page statement, delivered aloud to the Senate, suggested the cost of his vote will not be money but difficult decisions.