ALEXANDRIA, Sept. 22 -- Google faces a fresh federal court test today as US government lawyers ask a judge to order the breakup of the search engine giant's ad technology business.

The lawsuit is Google's second such test this year after the California-based tech juggernaut saw a similar government demand to split up its empire shot down by a judge earlier this month.

Monday's case focuses specifically on Google's ad tech "stack" - the tools that website publishers use to sell ads and that advertisers use to buy them.

In a landmark decision earlier this year, Federal Judge Leonie Brinkema agreed with the US Department of Justice (DOJ) that Google maintained an illegal grip on this market.

Monday's trial is set to determine what penalt...