The online sales house AdLink has acquired the media business of its biggest rival, DoubleClick, whose clients include MTV, in a £18.7m deal.

The two businesses will merge across Europe, with some redundancies likely, and marks the latest move towards consolidation in a sector decimated by the advertising downturn.

Retaining the AdLink name for the merged company, the former rivals have also signed an agreement to sell one another's sites in the US, where DoubleClick is the biggest player, and across Europe.

Adlink sells space on behalf of clients including Expedia, Yahoo and QXL.

DoubleClick will now concentrate on its technology and email marketing products, although it will retain a stake in the new company.

It will be the biggest operator in Europe, claiming to be able to reach 50% of all internet users through its sites.

"This transaction allows us to achieve the critical mass we need for our business model," said AdLink's chief executive Michael Kleindl.

"Stability, financial strength and scale in the form of increased reach and better service offerings are crucial in our business today."

Last month rivals Real Media and 24/7 Media merged to create another ad sales network spanning the world. The two new companies will now go head to head for the right to represent the largest sites.

Online ad sales was a growth industry during the dot.com boom as advertising cash rolled in and the sales houses expanded rapidly. But with the advertising downturn and the collapse of many client sites, most were forced to close or seek mergers.

Stephane Cordier, the vice-president of international media at DoubleClick, is expected to join the AdLink board as chief operating officer.

DoubleClick's chief executive, Kevin Ryan, said: "The transaction establishes a leading online media entity in Europe and allows DoubleClick to focus its European business on expanding its technology and email offerings."