Labor will support the government’s plan to accelerate tax cuts for small and medium businesses, in the first major policy win for Scott Morrison since he became prime minister.

Labor recently made several big policy announcements on education spending and early childhood; Morrison returned with a proposal to bring forward a planned 25% tax rate for businesses with a turnover of between $10m and $50m by five years, to July 2021.

Labor had committed to the government’s plan to lower the company tax rate for those businesses from 30% to 27.5%, but had not guaranteed a future Labor government would follow the plan the Senate passed, which originally would have seen the 25% cut take effect in 2026.

The government proposal, which had the support of the bulk of the crossbench but was rejected by the Greens, wedged Labor into stating a policy position.

But Chris Bowen said shadow cabinet had met, looked at the figures and had agreed to support the measure, expected to cost $3.2bn over the next four years – but would do it “responsibly”.

“The government yesterday announced a tax plan with no offsets, and said it will be paid for out of economic growth and surplus – a clear breach, a clear breach of their own budget rules, which say that improvements to the economy will go to the budget bottom line,” Bowen said.

“In the interests of certainty of smaller businesses, we will vote the legislation through the parliament and commit to the same tax rates for small and medium enterprises under a Labor or Liberal government,” Bowen said.

“A Labor government, will, when it comes in, also have access to the Australian investment guarantee. So in fact, Labor is offering a better tax offering for businesses than the government.

“We have made the tough decisions consistently now, for five years, tomorrow being the fifth anniversary of Bill’s leadership.”

Bowen said Labor would delay implementation of its Australian investment guarantee – a proposal that would allow businesses better tax offset opportunities when investing in new technologies – by one year to pay for the change if it won government.

Standing next to Bowen for the announcement, Bill Shorten was quick to dismiss the idea Labor had surrendered to the government on tax by offering its support.

“We are determined to restore people’s faith in politics,” he said. “That means sometimes, not simply opposing an idea became someone else had it.

“If the government says it has a view that business wants to have a slightly lower tax rate, earlier than the government was otherwise planning, we are prepared to compromise in the national interest.

“This is the sort of government I intend to lead. So what you might describe as perhaps just as politics, I see us as getting beyond politics.

“Where there is a good idea, Labor will see if we can make it work.”

Labor offered bipartisanship with the Morrison government to increase penalties for food tampering over the discovery of needles in strawberries, but its support of the accelerated tax pan is the first show of major policy bipartisanship.

But Bowen ruled out offering any support for any future plans the Coalition may have for tax cuts for big businesses, which it was forced to abandon after losing the support of One Nation and failing to convince other crossbenchers to support the legislation, in the Senate.

“I know that if the Liberals get re-elected, they will be back, renewed and energetic to give tax cuts to large companies,” Bowen said. “We will not.

The government plans on introducing its accelerated business tax cut plan to parliament when it resumes next week.