The Milton Keynes squad have endured a season to forget thus far, with the former multiple winners of the Constructors' Championship left slogging it out in the midfield, unable to bridge the gap to front-runners Mercedes and Ferrari, or even Williams.
Daniel Ricciardo's two sixth-place finishes are the best that Red Bull have mustered this term, and having seen both of his drivers lapped during Sunday's Spanish Grand Prix, Horner conceded that they are not even competing at present.
"It is not enjoyable being in a Grand Prix like today when you are just going around, you're not racing," Horner told reporters after the race. "We want to get back. The frustration is that not all of it is in our hands. We are relying on our partner."
Horner has urged Renault to focus on improving the performance – not the reliability – of their engines as they desperately look for a boost.
The French manufacturer has come in for heavy criticism from Red Bull for their failure to produce an engine that is capable of mixing it up at the head of the pack and to make matters worse, reliability has also been an issue for Red Bull, with Daniel Ricciardo already onto the final engine of his permitted allocation, meaning that grid penalties later in the season are inevitable.
Ricciardo saw his preparations for Sunday's race in Barcelona compromised by Renault's request not to do too many miles on the engine, and Horner believes that it is performance that should be Renault's focus.
“We are so far on the back foot with reliability anyway that, to be honest, this year is pretty much a write-off,” Horner said.
“You just have to go for it, even if they end up using 20 engines, it would be better to learn and make progress for next year. It would be far easier to make a fast engine reliable than to make a reliable car fast, so our philosophy has been to push performance.
“I think they know what the deficit is. The question is how are they going to make that up. They have things in the pipeline and things for later in the year but it is all a work in progress.
“I think they are looking at different scenarios and solutions, but they haven’t got a definitive direction yet. Hopefully they are homing in on it and things in the engine world take longer than in the chassis world.”