“ECSTATIC” is how Google chief executive Eric Schmidt described his reaction to the internet giant’s first-quarter results.

Google routinely beats analysts’ estimates, but even by its own high standards the first three months of this year proved exceptionally rewarding. The online search company made a net profit of $1 billion (£500m), up 69% from a year ago on a 63% jump in sales, to $3.66 billion.

It has been a big month. Last week Google announced a deal with Clear Channel, the world’s biggest radio company, to expand its advertising business on to the airwaves.

The week before, Google shelled out $3.1 billion to buy online ad company Double Click. The price was 20 times Double Click’s estimated revenues of $150m and triple the amount that private-equity firm Hellman & Friedman spent when it purchased the firm in 2005.

Google can afford it. For a company worth close to $147 billion Double Click is relatively small change. The real cost may come from how angry the move has made the competition.

The beaten bidder for Double Click was Microsoft, which seems to be forever playing catchup with Google. It is spearheading an effort to have Google hauled up on antitrust charges over the Double Click purchase.

Microsoft’s general counsel Brad Smith issued a statement in which he said the proposed acquisition “raises serious competition and privacy concerns in that it gives the Google/Double Click combination unprecedented control in the delivery of online advertising, and access to a huge amount of consumer information by tracking what customers do online”.

He added: “We think this merger deserves close scrutiny from regulatory authorities to ensure a competitive online advertising market.”

Microsoft executives have reportedly also talked to AT&T, AOL and Yahoo about similar concerns.

Both Microsoft and AT&T have faced antitrust charges in the past, with Google co-founder Sergey Brin calling Microsoft “a convicted monopolist”.

The irony was lost on no-one, especially Schmidt.

“Microsoft. Did you say Microsoft? And AT&T? Microsoft and AT&T? What is the year? They are wrong. Come on, they are wrong. Give me a break,” Schmidt said last week.

But it’s not only Google’s arch enemies who have their concerns. Advertisers also fear a combined Google and Double Click will have a negative impact on the advertising market.

On Friday, Sir Martin Sorrell, head of WPP and one of the most powerful voices in advertising, told Reuters: “I think the Double Click acquisition clearly raises some regulatory issues which a number of media owners, publishers and competitors like Microsoft are very exercised about.”

To date, Google has specialised in online search and accompanying relevant “contextual” text ads. Double Click’s exper-tise is in more sophisticated “targeted” banner ads, including pop-ups. Double Click doesn’t buy and sell ads, it acts as a technology platform between the advertiser, its agency and the site taking the ad. It also provides tracking to measure how successful ads have been.

For example, if BMW wants to place an ad campaign with the Times Online website, it would ask its buying agency to negotiate placing and price. The agency would choose Double Click or a rival to perform the back-office work and ensure the ads are properly displayed. Double Click would also monitor their effectiveness, counting how many times they had been looked at and clicked on.

Paul Mitchinson, UK managing director of DGM, an online-marketing specialist, said there was growing concern in the advertising community about Google’s online dominance.

“Google has positioned itself as the friendly interface to the internet, but there are growing signs that it is behaving in a monopolistic manner like Microsoft. The two companies are increasingly similar,” he said.

Online advertising remains a relatively small part of the overall advertising market - £2 billion out of a total of £17 billion in the UK, said Mitchinson. But it is growing rapidly — by 41% last year.

He said he was particularly concerned that Double Click’s third-party tracking would now be controlled by Google.

“A lot of our clients have already had discrepancies between the number of clicks (per online ad) that Google has charged them for and the number they reach by their own assessments,” said Mitchinson.

Schmidt argues that Google’s position in the online ad market has been exaggerated. But eventually success on Google’s scale is bound to bring regulatory scrutiny, merited or not.