Google argued that it was too financially burdensome and logistically challenging to compile and hand over salary records that the government has requested, sparking a strong rebuke from the US Department of Labor (DoL), which has accused the Silicon Valley firm of underpaying women.

Google officials testified in federal court on Friday that it would have to spend up to 500 hours of work and $100,000 to comply with investigators’ ongoing demands for wage data that the DoL believes will help explain why the technology corporation appears to be systematically discriminating against women

Noting Google’s nearly $28bn annual income as one of the most profitable companies in the US, DoL attorney Ian Eliasoph scoffed at the company’s defense, saying, “Google would be able to absorb the cost as easy as a dry kitchen sponge could absorb a single drop of water.”

The tense exchanges in a small San Francisco courtroom emerged in the final day of testimony in the most high-profile government trial to date surrounding the intensifying debate about the wage gap and gender discrimination in the tech industry.

The DoL first publicly accused Google of “systemic compensation disparities” during a hearing in April, saying a preliminary inquiry had found that the Mountain View tech firm underpays women across positions.

The current court battle stems from the DoL’s lawsuit filed against Google in January, accusing the company of violating federal laws by refusing to provide salary history and contact information of employees as part of a government audit. As a federal contractor, Google is required to comply with equal opportunity laws and allow investigators to review records.

Labor officials have said they uncovered pay disparities in a 2015 snapshot of salaries and that investigators needed an earlier snapshot and compensation history of the employees to better understand the wage gap. The agency has also argued that it needs contact information of employees so it can conduct confidential interviews.

Google would be able to absorb the cost as easy as a dry kitchen sponge could absorb a single drop of water DoL attorney Ian Eliasoph

“This is obviously a very time-consuming and burdensome project,” said Lisa Barnett Sween, one of Google’s attorneys, claiming that the company has already worked 2,300 hours at a cost of nearly $500,000 to partially comply with the government’s demands, which she argued were broad and unconstitutional. “Our courts must act to check this abuse of power.”

Google has vehemently denied the claims that it underpays women, claiming that it has closed its gender pay gap globally and that in the US it provides equal pay across races. Google has also argued that the DoL’s data request would violate the privacy of employees and fourth amendment rights against unreasonable search and seizure.

In one revealing exchange, Frank Wagner, the company’s director of compensation, admitted in court that if women are paid less than men in the same positions, those salary disparities can persist even if the employees perform at the same level.

Asked about a hypothetical, Wagner explained that if a female employee starts at a lower salary than a male colleague in the same job at Google, she may continue to make less even if they both excel in their first year and score the same on evaluations.

Wagner claimed that eventually, their wages would likely be adjusted to match each other: “There would be convergence over time.”

Eliasoph, the DoL attorney, said that it was outrageous for Google to argue that historical salary data was irrelevant to the government’s audit, considering it is widely understood that discriminatory wages lead to continued disparities as women advance in their careers.

“This claim requires putting one’s head in the sand with respect to 30 years of law on pay discrimination.”

Kristin Zmrhal, Google’s senior legal operations manager, also testified that the process of compiling data for the DoL has required engineers, lawyers and employees across departments to build new systems, conduct extensive quality reviews of files, redact documents and complete other complex tasks.

“It became too burdensome,” she said, noting Google was forced to hire a third-party vendor to help. “The team was bogged down.”

Eliasoph pointed out that Google has consistently earned millions in lucrative government contracts and has recently announced “with great public fanfare” that it invested $150m in diversity initiatives.

“Google cannot claim ... that it now has no money to comply with a federal agency seeking to ensure compliance with equal opportunity laws on behalf of the public.”

He also claimed that Google, with more than 21,000 employees, was trying to present itself as “too big to comply” and that the company should not be able to skirt anti-discrimination laws just because it is large and has a complex compensation model: “Google takes routine requests and makes them sound onerous by emphasizing the number of people involved.”

Sween asserted that Google has complied with the “overwhelming majority” of the government’s demands, adding, “The agency has little if any regard for the fourth amendment rights of its contractors.”

Earlier this month, the tech firm’s lawyers also unsuccessfully argued that the case should be dismissed altogether, claiming that a DoL official may have violated ethics rules by talking to the Guardian about the federal investigation.