In his budget-in-reply speech on Thursday, Mr Shorten vowed to cut the small business tax rate 5 per cent, write off the debts of 100,000 science, technology, engineering and maths graduates and lift investment research and development to 3 per cent of gross domestic product by 2025.

Business groups, the scientific community and universities welcomed Mr Shorten’s focus on science and technology speech but queried how Labor would find the money to pay for his promises.

Mr Shorten did not announced savings measures but pointed to Labor’s plan to raise $21 billion over 10 years by targeting multinational tax avoidance and reducing superannuation tax concessions.

He argued his measures would enhance productivity and generate long-term revenue.

Grattan Institute chief John Daley estimated that cutting the small business tax rate from 30 to 25 per cent would cost $3.5 billion a year — $17.5 billion over five years.

Universities Australia said the government would have to lift investment in research and development $4 billion a year to hit its 3 per cent GDP target.

A spokesman for Mr Shorten said the proposal to wipe the debt of 25,000 students a year from 2017 would cost about $1.4 bilion over a decade.

The Coalition yesterday attacked Labor’s estimated $45 million over four years to wipe the HECS debts of 100,000 graduates, arguing the true cost of the policy would be at least $2.25 billion.

Prime Minister Tony Abbott accused Mr Shorten of “magic pudding economics and of “peddling false hope”.

Shadow Treasurer Chris Bowen said Labor’s policies would involve more saving than spending over a decade.

Group of Eight universities chief Vicki Thomson said: “These are big-ticket items that will cost a lot of money. There is nothing we wouldn’t support but the question is, where is the detail?”

Ms Thomson said most students would study the course that interested them, regardless of cost because they do not have to repay debts until they earn a decent wage.

Grattan’s higher education director Andrew Norton said there was no evidence Australia had a shortage of science graduates — undergraduate enrolments rose 35 per cent from 2008 to 2013.

Recent figures showed the under-employment rate for recent life science graduates was more than 50 per cent — second worst behind the visual and performing arts.

“Labor’s latest policy is, unfortunately, only likely to encourage people to make choices that put them at high employment risk,” Mr Norton said.

Director of science policy at the Australian Academy of Science, Les Field, said investment in research and development was now about 2 per cent of GDP.

Lifting this to 3 per cent would involve a doubling — or even tripling — of investment over 15 years, he said.