PRIME Minister Malcolm Turnbull has accused Bill Shorten of taking a ‘backhander’ in his time as a union leader.

In a fiery start to Question Time today, Mr Turnbull accused the Opposition leader of ‘trading away’ Union members entitlements ‘for years’.

It comes after the Prime Minister announced new laws to crackdown on ‘secret payments’ to unions to be introduced to Parliament this week.

Speaker Tony Smith ruled the accusations were allowed because he did not believe that the Prime Minister was ‘literally’ suggesting Mr Shorten took a backhander.

The Prime Minister continued the personal attack on penalty rates, saying Mr Shorten had sold workers out “for a bag of gold”.

“The only time he can be relied upon to stick to his word is when it is coincidentally in his own interest at the time.

“He has no regard for the truth, no regard for accuracy, abandoning his commitments again and again.

“Mr Speaker, the fact is this, in terms of penalty rates, when the Leader of the Opposition had the power to determine penalty rates, when he was representing the workers and the Australian Workers Union, what did he do? He sold them out. He sold them out for a bag of gold.”

Earlier Mr Turnbull has opened up a fresh front on the industrial relations battleground, proposing news laws to jail union officials and employers who make “corrupt” secret payments.

As Labor leader Bill Shorten stood up in parliament today to introduce a private bill to protect the take-home pay of workers, the prime minister strode into a press conference at Parliament House alongside his Employment Minister Michaelia Cash.

The pair unveiled plans to penalise employers and union officials found to have made secret payments other than for clearly legitimate purposes. It would also require full disclosure of legitimate payments.

It continues the Turnbull Government’s bid to “restore the rule of law” to the Australian industrial sector after it passed laws to introduce an anti-corruption watchdog to police the construction sector late last year.

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“Secret payments are utterly unacceptable — trade unions have a solemn, legal, moral, fiduciary duty to act in the best interests of their members,” Mr Turnbull said.

“We have seen through the Heydon royal commission and subsequently unions have let their members down and big unions have traded their rights away in return for payments.”

For payments with the intent to corrupt, penalties include up to 10 years in prison and fines of $900,000 for individuals.

Sentences of up to two years and $90,000 would apply for other illegitimate payments.

Businesses would face fines of up to $4.5 million for making any corrupt payments to unions under the new laws to be introduced to Parliament on Wednesday.

Senator Cash said there was no consistency across Australia’s bribery laws and the offence was often difficult to prove.

“Employees should be aware and should have full knowledge of any payments that are made between their employer and a union,” she said.

“When you look at the level of penalty, it should send a very, very clear message to any employer or any union who wants to indulge in secretive payments.

“It is wrong and compromises the integrity and lawfulness of the workplace.”

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The pair described their announcement as a test for Mr Shorten.

But the opposition leader was already pre-empting the attack as he addressed parliament about his bill aiming to stop future cuts to penalty rates following the Fair Work Commission’s decision to align Sunday rates in the hospitality and retail sectors.

“What I say to the prime minister is use whatever distraction that you think is necessary. Use every possible dishonest distraction you have in your book. Put up whatever story you want,” he said.

“But on this issue, when it comes to defending working families in this country, the living standards of working families, we will not be deterred or put off.”

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Earlier Senator Cash accused Mr Shorten of selling out mums and dads.

“Small business needs a break,” Senator Cash said. “Small business needs to be able to compete on a level playing field with big business and big unions.”

“If Bill Shorten wants to continue to stand up for big unions and big business as he has done consistently whilst he have been in government --- look at the Road Safety Remuneration Tribunal. He stood with the TWU and big business against mum and dad truck drivers.

“The CFA. He stood with Peter Marshall and the UFU against tens of thousands of Victorian volunteers. In relation to the Australian Building and Construction Commission, he stood for the CFMEU and big business.”