Celebrity independents and a ­hostile crossbench are poised to stymie Malcolm Turnbull’s key election promises to cut company tax and restore the building industry watchdog if he wins today’s election, thwarting the Prime Minister’s intention of the double- dissolution election.

As voters abandon the major parties for indepe­ndents, voting reforms appear unlikely to end the horsetrading and chaos in the Senate, which could cruel the ­Coalition’s chances of passing its centrepiece promises.

As Mr Turnbull used his last day of campaigning to call again for stability and a vote for the ­Coalition in the upper house, ­betting markets and experts were predicting the new crossbench could have as many as 18 senators — the same as in the dissolved 44th parliament — which would include a new block of up to five candidates from the Nick Xenophon Team.

Of the 13 independents who could secure a place on the Senate crossbench, just three told The Weekend Australian that they supported the Coalition’s 10-year corporate tax plan and re-establishment of the ABCC.

GRAPHIC — Battleground seats

Contenders such as Derryn Hinch in Victoria and Pauline Hanson in Queensland are seen as probable new independent senators, likely to join a re-elected Jacqui Lambie and Senator Xenophon in parliament.

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GRAPHIC — Crossbenchers

The final result of the new ­Senate will not be known for up to five weeks, with the Australian Electoral Commission counting only first-preference votes on election night from both below-the-line and above-the-line voters. This is likely to indicate the make-up of about half of the new Senate.

Whatever the shape of the new crossbench, prospective senators are warning that passing contentious government legislation will be difficult. In the last parliament, the government needed the support of six of the eight Senate crossbenchers for its bills to ­become law if it did not have the backing of Labor or the Greens.

If the government has to rely on crossbenchers to get the ABCC through a joint sitting, in which both houses sit, it will have to work hard to win over independents, most of whom have a number of amendments they want included before offering their support.

Mr Hinch, who scored pole position on the Victorian Senate ballot paper, refused to back the government’s mandate yesterday, saying he was undecided on ­legislation to restore the ABCC and would have to be briefed on personal income tax changes.

He said he supported “in principle lowering the company tax rate, which the Coalition has presented as the centrepiece of its election campaign.

“I have to get elected first and see the colour of the legislation, he told The Australian.

Ms Hanson has said she ­needed to see the legislation to re-­establish the construction watchdog before firming her position and could not guarantee support for the company tax cuts, saying Australians needed personal ­income tax breaks first.

Senator Lambie was one of the most vocal opponents of the ABCC in the last parliament and did not respond to The Weekend Australian yesterday when asked if she would back personal ­income and company tax breaks.

Senator Xenophon has supported company tax cuts for businesses with an annual turnover of up to $10 million, but has not committed to the government’s 10-year plan, under which the cut is gradually extended to the biggest companies. Another three potential crossbenchers — Zhenya Wang, Glenn Lazarus and John Madigan — are opposed to company tax cuts for businesses earning more than $10m.

Liberal Democrat David Leyonhjelm and Family First’s Bob Day, previously supportive of the Coalition’s agenda, warned the relationship could be tested unless the government improved its negotiating skills.

Senator Leyonhjelm said it would be “worse than it was before if the Coalition was re-­elected. “If it’s a Labor govern­ment I think they’ll do much better, but I don’t think that will happen, he said.

One potential new senator — the Sex Party’s No 1 NSW candidate Ross Fitzgerald, a columnist for The Weekend Australian and, according to Sportsbet, sitting on $2.25 to win a seat — said he would support the mandate of whichever major party won.

The Sex Party’s lead candidate in Victoria, Meredith Doig, said the party did not want to be “blockers in the Senate and would negotiate in good faith with the government of the day.

John Wanna, who holds the chair of public administration at the Australian National University, said he was predicting a ­slightly smaller crossbench of about 15 comprising fewer Greens, about four senators from the Nick Xenophon Team, Jacqui Lambie and two other independents.

He said the new Senate reforms would make it harder for minor parties previously dependent on preferences to be elected, but those with high profiles could secure a position in parliament based on the primary vote.

Australia Institute executive director Ben Oquist said he was predicting 31 Coalition senators, 26 for Labor, nine for the Greens and five for Nick Xenophon, with four other independents.

Sarah Martin & Rosie Lewis, The Weekend Australian, July 2-3, 2018, p 1 and 8