Google will on Tuesday launch a customisable search engine that users can carry on their own blogs and other websites, a move that potentially opens up a big new market for its search listings and related advertising.

Marissa Mayer, vice-president of search products and user experience, said it was the most significant launch that Google would announce in the final months of this year. By letting companies and individuals build their own specialised search engines, it will also create competition for the many new “vertical” search products that have recently been launched on the web, she added.

These sites, which deal with narrow areas of interest from job vacancies to information technology, have become one of the industry’s big new growth areas.

Users of Google Custom Search Engine will be able to select the websites they want to be included in their searches, and add to this list in future by “tagging” websites they visit. Any searches will then return results just from that slice of the Google search index.

Google also said it had created an easy way for users to “paste” a search box for the personalised engine on to their own webpages, so that visitors can carry out searches using their preferred parameters.

Results to those searches will also carry context-relevant advertising from Google’s AdSense network.

Any revenue from the advertising will be shared with website owners on the same terms that Google offers to existing publishers that carry its search results, executives said.

The ideas behind Google’s personalised search engine echo experiments tried by some other “Web 2.0” companies. Rollyo (short for Roll Your Own Search Engine) offers a similar service.

Google shares set a fresh lifetime high of $480.78 on Monday that followed last week’s report of surging financial growth and Wall Street’s upgrades on the stock, Reuters reports.

Shares jumped 4.6 per cent to close at $480.78 on Nasdaq, surpassing an intraday trading high of $475.11 set on January 11 2006. The stock fell to lows around $330 in March.