Labor has called on Malcolm Turnbull to review a proposal to water down Tasmania’s gun laws and lobby the Liberal state government to abandon them, if necessary.

In a letter to the prime minister on Friday, Bill Shorten said that the Hodgman government’s policies represent a “direct threat to [the] essential national consensus” achieved by the national firearms agreement.

The changes – released to shooting groups and farmers and revealed just the day before the election – include extending the limit on gun licence duration from five to 10 years and abolishing mandatory weapon removal for minor breaches of firearm storage laws.

Shorten said that he was “concerned by reports on the eve of the recent Tasmanian state election that the Hodgman government had secretly committed to water down that state’s gun laws”.

“Simply put, the weakening of gun laws threatens the safety of our community,” he said. “I ask you to order an immediate review into the compliance of the Tasmanian government’s proposal with the national firearms agreement.

“If, as appears to be the case, that proposal would breach the agreement, I ask you to publicly demand that your Liberal party colleagues in the Tasmanian government abandon it.”

With record marches and civic activism calling for gun control in the United States, the federal Coalition government in Australia has been criticised for considering creating a “firearms advisory council”, which the gun lobby says would give it “a seat at the table” for consultation.

After his re-election in Tasmania Will Hodgman defended the Liberal government’s controversial guns policy, arguing it would not breach the national firearms agreement and suggesting it might be changed before it is introduced to parliament.

“We will engage with our colleagues on a national level to ensure there is no breach of the national firearms agreement,” Hodgman said. “It will not happen.”

The prime minister’s office referred a request for comment to the minister for law enforcement, Angus Taylor.

Taylor said the Turnbull government “has no intention to change the national firearms agreement” and noted Hodgman had committed “not to do anything to compromise the agreement”.

“Shorten’s letter is simply another political stunt from Labor,” he said. “If Labor were serious about tough gun laws, they would have backed the Turnbull government’s legislation to impose minimum mandatory sentences for illegal gun traffickers instead of voting them down.”

In other changes revealed in a 9 February letter to a firearm consultation group, the Tasmanian government said it would allow greater access to category C firearms – such as self-loading rifles and pump-action shotguns – for farm workers and sporting shooters.

On Sunday the Liberal Democrat senator David Leyonhjelm told ABC24 the proposed changes were “not much of a weakening” of gun laws.

He cited a proposal that where farmers are already allowed to use certain types of firearms, the workers on those farms should be able to use the same weapons, saying it “makes an awful lot of sense”.

“Bill Shorten can huff and puff all he likes about it, at the end of the day if a state decides they don’t want to cooperate with the national firearms agreement, that’s up to them,” Leyonhjelm said.

The Liberal Democrat said he thought it was “very good politics” for Hodgman to release the policy to firearms owners and licensees “who are prepared to vote on that issue”.

Those who “who jump up and down about gun laws being too weak and wanting more controls and so on” don’t vote on the issue, he claimed.

Leyonhjelm – a recipient of donations from the gun lobby – said Shorten risked alienating 1 million gun owners who would see “this is a confected story that has nothing to do with safety”.