The European Commission may crack down on Google, Yahoo!, Microsoft et al and tell them they can’t keep personal search data longer than six months – and even that may be pushing it.

The EC’s international advisory body, the Article 29 Data Protection Working Party, whose findings are usually adopted, delivered its 29-page opinion to the regulator last Friday and it ain’t buying Google’s dearly held arguments of better search results or custom tailored ads.

In fact it says, ignoring all the defenses mounted so far, that the search firms “have so far insufficiently explained the nature and purpose of their [data collection] operations to the users of their services” and reasoned that the fact Google last year, when the heat was on, voluntarily reduced its cookie retention to two years from forever goes to show that the “previous terms were longer than necessary.”

The 29ers consider web addresses and cookie monitoring personal information and want identifiers disassociated from search queries, an idea anathema to Google.

They also harbor the old-fashioned notions that web sites should be able to opt out of being crawled, indexed and cached and that user permission should be sought before correlating their data, creating profiles and delivering personalized ads.

In response, Google’s global privacy counsel Peter Fleischer blogged its rationale but said nothing new. At this point, Google is expected further discussions with the powers that be.

Microsoft says it destroys information after 18 months. Google and Yahoo “partially anonymize” after 18 and 13 months respectively.