Google’s fast-growing tool for searching job listings has been a boon for employers and job boards starving for candidates, but several rival job-finding services contend that anti-competitive behavior has fueled its rise and cost them users and profits.

In a letter to be sent to European Commissioner for Competition Margrethe Vestager yesterday and seen by Reuters, 23 job search Web sites in Europe called on her to temporarily order Google to stop playing unfairly while she investigates.

Similar to worldwide leader Indeed and other search services familiar to job seekers, Google’s tool links to postings aggregated from many employers. It lets candidates filter, save and get alerts about openings, though they must go elsewhere to apply.

Alphabet Inc’s Google places a large widget for the two-year-old tool at the top of results for searches such as “call center jobs” in most of the world.

Some rivals allege that positioning is illegal because Google is using its dominance to attract users to its specialized search offering without the traditional marketing investments they have to make.

Other job technology companies say Google has restored industry innovation and competition.

The tensions expose a new front in the battle between Google and online publishers reliant on search traffic, just as EU and US antitrust regulators heed calls to scrutinize tech giants, including Google.

Google has so far withstood similar accusations from companies in local business and travel search over the past decade.

Vestager, who has been examining job search on Google, leaves office on Oct. 31.

However, a person familiar with the review said Vestager is preparing an “intensive” handover so that her successor does not drop it.

Her office declined to comment on the handoff.

Lack of action could spur the signatories, which include British site Best Jobs Online to German peers Intermedia and Jobindex, to follow with formal complaints against Google to Vestager, a person familiar with the matter said.

Berlin-based StepStone GmbH, which operates 30 job Web sites globally, and another German search service already have taken that step, another person said.

Google long has been frustrated by other search engines filling its results, because they both add a step in users’ quest for quick information and pose a threat to its ads empire.

Nick Zakrasek, senior product manager for Google search, said that the company welcomed the industry feedback on jobs search.

Google said its offering addresses previous antitrust complaints by allowing rival search services to participate and includes a feature in Europe designed to give rivals prominence.

“Any provider — from individual employers to job listing platforms — can utilize this feature in search, and many of them have seen a significant increase in the number of job applications they receive,” Zakrasek said in a statement.

“By improving the search experience for jobs, we’re able to deliver more traffic to sites across the Web and support a healthy job search ecosystem,” he said.

Google’s widget drew 120 million user clicks in June in the US alone, about double from August 2017, according to research firm Jumpshot, which receives browsing data from antivirus apps.

Eric Liaw, a general partner invested in workplace tech start-ups at Silicon Valley’s Institutional Venture Partners, said Google has “to be careful about how much air they suck out of the room given the scrutiny they are under.”