Prime Minister Anthony Albanese has heaped ridicule on a Coalition policy that would allow businesses to write off lunches on tax.

The federal government released an analysis provided by Treasury which showed the policy would cost between $1.6 billion and $10 billion a year.

Albanese exclaimed it was “the worst, sloppiest policy put forward by any Opposition that I’ve seen in my entire time since I’ve been in parliament”.

“This shows they are simply not fit as an alternative government.

“They have opposed every cost-of-living measure and this is all they’ve come up with.”

But what started as a debate over the cost of lunch soon devolved into accusations of dishonesty and a breach of the public service code of conduct.

Shadow treasurer Angus Taylor claimed the government’s releasing of the figures was an “egregious politicisation of the public service”.

It forced the hand of the Opposition, which revealed its own analysis, produced by the independent Parliamentary Budget Office, had costed it at less than $250 million.

Treasury secretary Steven Kennedy should provide a “full explanation” as to how it came about, Taylor said.

“We have a long-standing custom in this country of not politicising the public service,” he said on Tuesday.

“But it is very clear today, the Treasurer is intent on doing exactly that.”

Chalmers said the government had a duty to provide Treasury’s costings to the Australian people because the Coalition had not been forthcoming with its own figures.

The policy to allow businesses to claim up to $20,000 a year on meals and entertainment was announced two weeks ago.

“I heard Angus Taylor was losing it this morning on TV,” said Chalmers.

“To be frank with you, I would rather not have to do it.

“I would rather a responsible opposition provided the costings of their policy and told Australians what they were going to pay for it. That hasn’t happened.

“Part of my job is to understand risks to the budget, and this is a very substantial risk to the budget.”

The PBO was set up in 2012 to provide non-partisan analysis of policy, in part to prevent the risk of governments weaponising Treasury to discredit opposition proposals.

Taylor argued the parameters the Albanese government provided Treasury were different to those assumed by the Coalition, thereby providing a dishonest representation of the policy.

“Steven Kennedy will need to answer why he has done this and how this is not a breach of the Australian Public Service Code of Conduct,” he told Sky News.

But former Treasury secretary Ken Henry said public servants being accused of contravening their obligations to objectivity was nothing new.

“If the Treasury secretary is requested to do a piece of work for the government, and it’s lawful, then the Treasury secretary should do it,” he said.

“I was frequently accused of having engaged in some activity which was seen as being political, rather than a piece of dispassionate analysis.

“But it’s all rubbish. It’s just part of the way that political debate is conducted in Australia and, unfortunately, I don’t think we’re going to change it.”

-with AAP