The number of employees of major companies who claim to have witnessed illegal contributions to public officials is four times higher than it was two years ago, according to a new study from a business ethics watchdog group.

Four percent of 4,600 private-sector employees surveyed this fall by the Ethics Resource Center said they witnessed improper contributions to campaigns and parties. By comparison, only 1 percent of respondents reported these transgressions in the group’s previous study, completed in 2009.

“If these numbers are quadrupling, it is eye-popping,” said Kenneth Gross, a lawyer with Skadden, Arps, Slate, Meagher & Flom’s political law practice who advises corporate clients on government affairs compliance. “Possibly the relaxed laws on giving have pervaded … the workplace, giving people the impression that things aren’t as strict as they were.”

Although it is not clear what led to the spike, there is no question that the Supreme Court’s 2010 decision in Citizens United v. Federal Election Commission, which opened the door to unlimited political spending by unions and corporations, has dramatically changed the landscape of political giving in the business world, heightening pressure on fundraisers to rake in big sums from new sources.

Manager-level employees at publicly traded companies were most likely to report observing an illegal contribution, according to data the organization prepared exclusively for Roll Call. Seven percent of senior managers reported observing illegal contributions.