LONDON, England - Red Bull raised concerns with Renault about the direction of its engine programme as far back as 2012, team principal Christian Horner has claimed.The French supplier of Formula 1 engines has had a problem-plagued start to the new V6 turbo hybrid era while Mercedes has dominated the 2014 results since the first race in Australia in March.Horner was heavily critical of Renault after June 2014's Austrian GPduring which Red Bull's four-times F1 champion Sebastian Vettel retired and team mateDaniel Ricciardo finished eighth. He described their engines' performance as "unacceptable"RENAULT ERRED"We raised our concerns as far back as the end of 2012 with the direction the project was going," Horner told reporters ahead of this weekend's (July 6) British GP,"but designing and building engines is not our core competence... and I don't think any of us could have envisaged that Renault would be as far behind as it is."Horner suggested Renault - which supplied four teams for 2014 - had erred in not focusing development of the power unit around one car, as Mercedes and Ferrari had. "When you look at the engine Ferrari has made the customers have had to adapt their cars accordingly."Mercedes likewise, whereas Renault tried to keep all its customers happy, an admirable thing to do but not the best way to be competitive."