Bernie Sanders has slammed Donald Trump’s "job-saving" deal with Carrier as it demonstrates other companies could receve similar benefits for outsourcing jobs.

In an op-ed for The Washington Post, the former presidential candidate said Mr Trump had promised to save all US-based jobs at the air conditioning plant from moving to Mexico, and to make parent company United Technologies "pay a damn tax". Instead, Mr Trump saved less than half of the 2,100 jobs and is reportedly offering the company a tax cut.

"Let’s be clear: It is not good enough to save some of these jobs," wrote Mr Sanders.

"Trump made a promise that he would save all of these jobs, and we cannot rest until an ironclad contract is signed to ensure that all of these workers are able to continue working in Indiana without having their pay or benefits slashed."

The president-elect previously threatened to make companies pay big tariffs for leaving the country and selling foreign-made products back to the US. He tweeted on Thursday morning that he was traveling to Indiana to meet the “hard working and wonderful people” at the company.

"In essence, United Technologies took Trump hostage and won. And that should send a shock wave of fear through all workers across the country," said Mr Sanders, adding that Mr Trump might exchange more jobs being sent offshore for business-friendly tax incentives.

Mr Sanders said he will introduce the Outsourcing Prevention Act to prevent future deals.

United Technologies made a profit of $7.6 billion in 2015 and received more than $6 billion in defense contracts, he said. Former chief executive Louis Chenevert was awarded $172 million, and the company’s five highest-paid executives were given more than $50 million.

"Does that sound like a company that deserves more corporate welfare from our government? Trump’s Band-Aid solution is only making the problem of wealth inequality in America even worse," the Vermont senator wrote.

Mr Sanders proposed that companies pay an outsourcing tax equal to the amount of money it would save by moving factories to Mexico or other low-wage countries, and should not receive federal contracts or "corporate welfare" from the US government.

He also spoke against rewarding executives with stock options and bonuses, using company money to inflate their stock price - as Carrier spent billions of dollars doing - or paying large sums to employees for outsourcing to low-wage countries.

"If Donald Trump won’t stand up for America’s working class, we must," wrote Mr Sanders.

The president-elect previously said he had "worked hard" to prevent Ford from moving its production plant to Mexico.