The federal government will intervene to let Toyota workers vote on proposed changes to its industrial relations policy, the employment minister, Eric Abetz, said.

Toyota is appealing to the federal court after it lost a case last December seeking to allow employees a vote on adding various clauses to its enterprise agreement.

Among the clauses are reducing the "Christmas shutdown" period from 21 days to 10 days, reducing the number of days of paid leave to attend union delegate training from 10 days a year to five days in the first year and two days in subsequent years, and removal of paid "wash-up time".

Toyota claimed the clauses were necessary to compete with plants in other countries, but a group of Toyota workers argued in court it was in breach of the enterprise agreement.

The government has offered support for the changes – with the treasurer, Joe Hockey, last week claiming the union was “at war” with Toyota – and it has now decided to join the federal court appeal.

"It is clearly in the public interest that the workers be allowed to vote on Toyota's proposed variations and determine their own destiny," Abetz told guests at the Sydney Institute on Tuesday.

"Tonight I announce that I have decided to intervene in support of Toyota's workers being allowed a say as soon as possible on the proposed variation."

He said the clauses should not have been proposed for the agreement in the first place.

Abetz said 1586 working days, or about $370,000 in wages, are lost by a clause that would allow a half day on the last day before shutdown.

If all 69 of the company's union delegates took the full 10 days' paid leave for education activity, this resulted in 690 working days lost, or about $150,000 in wages, he said.

"These are just two instances of how more than 2000 working days’ worth of productivity could be re-injected into Toyota immediately," he said. "Management needs to accept responsibility. But it is deeply troubling that the employees' right to vote on proposed variations has been frustrated."

The acting AMWU national secretary, Paul Bastian, told Guardian Australia it’s “not surprising” to hear this announcement by Abetz, and accused the government of shifting blame.

“If we look back at the extraordinary events last week, the treasurer of this country and the industry minister trying to shift the blame for the demise of the auto industry on to the back of workers … it’s not surprising that they would make this move,” Bastian said. “We’re not going to sit back and cop the government trying to cop out.”

Bastian said Toyota was exercising its rights under legislation by appealing against December’s decision, just as workers did, but the dispute won’t be resolved in court.

“The union took a position that we had rights under the agreement and we sought to enforce those rights. Toyota is now seeking to appeal. In terms of the issues – they are a matter for negotiations and we are open for negotiations,” he said.

“This issue between the parties will be resolved around the negotiating table, sitting down as equals.”

Abetz also used his speech – titled "industrial relations after the 30 years war" – to criticise the previous Labor government's economic record.

He accused the Labor leader and former industrial relations minister Bill Shorten of granting "an unseemly range of union wish-list claims", while the former prime minister Julia Gillard played "Santa Claus" to union demands.

"Every union boss, like a child writing to Father Christmas, presented their wish list to the government, which was duly granted," he said.