Laid-off bankers are griping that Goldman Sachs used chilling, underhanded tactics as it mounted this week’s bloodbath that claimed more than 3,000 employees, The Post has learned.

Insiders claim the Wall Street giant — whose Wednesday layoffs were dubbed “David’s Demolition Day” after CEO David Solomon — emailed calendar invites that called targeted employees to phony business “meetings” at its New York headquarters.

But once the employees arrived in a conference room — many of them for meetings as early as 7:30 a.m. Wednesday — they were greeted by the head of the team telling them they were getting canned and their manager grimly observing the proceedings.

“He got here early for the meeting and was told the news,” one source said, recounting the sad tale of a colleague who had been fired. “Meeting was put on his calendar under false pretenses.”

“Managers were sorry to do this but their hand was forced and they wished him the best of luck,” the insider told The Post.

Another employee was told to arrive at 7:30 am for a call with Goldman counterparts in the Asia-Pacific region and didn’t question the early meeting since those with other regions are typically during “off-hours,” another source said.

Fired employees were given the choice to leave the office immediately or wait for colleagues to arrive so they could say goodbye. Most of the casualties chose to exit the building following a wave of axings that were done before 9 a.m.— leaving colleagues who filtered in afterwards confused over what had happened, sources said.

Indeed, the cold efficiency of the proceedings took on a more chaotic feel as  many managers weren’t clear about next steps, including when health insurance coverage would end or how much severance fired employees would receive.

That’s partly because the human resources department was among the units that were hard hit by the firings, and lacked the headcount to properly administer the meetings, insiders said.

“When he asked questions… they had no details and asked him to confirm his personal cell and email and that someone ‘would get back to him later,” the source added. “Typical for our human capital management (Goldman’s Human Resources) … they are a sloppy mess on everything administrative.”

A Goldman spokesperson denied HR cuts had an impact on communicating severance and pushed back against the notion that the firings were a surprise. Solomon had warned over the last few months that cuts were coming and the company said they would begin Wednesday.

“We know this is a difficult time for people leaving the firm. We’re grateful for all our people’s contributions, and we’re providing support to ease their transitions,” Global Head of Communication Tony Fratto said in a statement.

Another source noted Goldman treated managing directors and vice presidents with more transparency – giving them warning they might get cut over the past few weeks before a final decision had been made.

Higher-level Goldmanites didn’t have much sympathy for those blindsided by getting fired after receiving a rogue calendar invite. One employee who’d been in finance for well over a decade told The Post sending a calendar invite to someone as a ruse to get them one on one and then lay them off is “pretty standard.”

“If someone didn’t see that coming… that’s on them,” the employee added.

Younger employees in other industries seemed unaware Goldman used a common tactic to fire people.

One frantic employee at data company Dremio posted on corporate message board Blind, which verifies users’ place of employment with the help of their company email accounts, they were the only one of their colleagues to receive an invitation from their manager for a 15-minute meeting.

 “I’m so worried… How likely it could be a layoff?” the employee asked.

More seasoned employees chimed in, “Yes it’s a layoff. Decision has already been made.”

Another Blind user said, “You are laid off. Clean personal off your laptop. Collect anything you want to save like contact info for references.”

The Dremio employee hasn’t posted an update about their employment status since.