Heineken Cup review:Biarritz put a dent in Bath's hopes of emerging from Pool Four of the Heineken Cup when inflicting a one-point defeat on the English side at The Rec, but Wasps claimed a valuable bonus away to champions Toulouse.
David Skrela scored all of his side's points with six penalties in wet conditions in the south of France.
Wasps scored the only try through substitute David Lemi in the second period while David Walder had the chance to win the tie with a last-gasp penalty but outhalf pulled his kick wide of the posts and four-time champions Toulouse held on.
Basque side Biarritzare now second behind Ulster, who beat Aironi Rugby 30-6 at Ravenhill on Friday night. France international scrumhalf Dimitri Yachvili kicked four penalties to wipe out Bath's early 8-0 lead and clinch a potentially priceless Pool Four away win.
Bath exited at the group stage last season and they are already battling to avoid a repeat despite starting promisingly through skipper Michael Claassens' try and an Olly Barkley penalty.
Biarritz, beaten by Toulouse in the Heineken final last term, ground Bath into submission and left Yachvili to do the rest, with his clinching penalty struck immediately after Bath prop David Wilson was sin-binned 10 minutes from time.
Bath had chances to give Barkley a late drop-goal chance, but they faltered under pressure and Biarritz possessed the nous to close out the game.
Bath boss Steve Meehan claimed his team needed to "grow up" after the defeat.
"It's actually quite difficult to put into words," said head coach Meehan. "We played a very good first half - we got all the decisions right - but a few technical penalties went against us in the second half.
"And then with four minutes to go, we had an opportunity to win the match, but we didn't take it. It was a better performance than last week (against Gloucester), yet to come up short like that is very frustrating."
Meehan added: "Biarritz were happy to live off our penalties to begin with in the second half. They ticked over three points at a time.
"We've got to grow up and take the points. It's straightforward, it is about being ruthless, getting the job done and getting it (the ball) through the sticks. Simple.
"Drop-goals and penalties win games. They (Biarritz) kick the penalties and keep the scoreboard ticking over. We had the opportunity and didn't take it."