Renault's chief of engineering Pat Symonds admits his team's performance at the start of the season has left him disappointed.
The French squad had high hopes for 2009 following a very strong final part of the 2008 season, when Fernando Alonso scored two wins in Singapore and Japan.
However, the R29's performance has been below par so far, and Renault has scored just five points in the first four races.
Symonds says he was expecting a much stronger start to the season.
"I'm disappointed with our start to the season," said Symonds. "We're all well aware of the difficulties of trying to assess competitiveness through winter testing, but when we arrived in Melbourne we did feel we were higher up the pecking order than the performance we actually delivered. However, what has impressed me is how the whole team has responded to the need to become more competitive, particularly following the clarification of the diffuser regulations as we managed to get the new-style diffuser onto one of the cars in China, which is a credit to the whole team.
"So it has been a disappointing start, but we've definitely moved up the order in the last four races and there's a lot more to come."
Symonds is adamant, however, that Renault will make significant progress from this weekend's Spanish Grand Prix, thanks to new parts and the continued development of the double-decker diffuser introduced in China.
"The whole team is still pushing hard with development and the diffuser and floor that we brought to China was very much a first attempt and over the course of the year we will see several more versions, the first of which we hope to have in Barcelona," he added.
"In addition, we've got new wheel fairings this weekend with quite a major design change to give us an increase in downforce and a new rear wing. On top of that we've got a few small aerodynamic tweaks that we will introduce on a race-by-race basis. Overall we can expect a reasonable step in performance for Barcelona."
Alonso, meanwhile, is aiming to score "big points" in his home race after two disappointing outings in Spain last year.
"It's always very special to race in Spain and I'm lucky to have two races at home this year in Barcelona and Valencia," he said. "Seeing the support of the fans always gives me a boost and I just hope that I can make them happy and have a strong weekend.
"It will be difficult to fight for the podium, but hopefully we can qualify well and score some big points in the race."