Christian Horner insists the Red Bull chassis only makes a 15-20 per cent contribution to the team's current difficulties, despite increasing critique from Daniel Ricciardo that his lack of pace is not just down to the much maligned Renault power unit.

The Australian has made repeated claims that Red Bull's current lack of competitiveness is more equally divided between the RB11's chassis, as well as its underpowered Renault engine, but Horner has maintained a public view that the lacklustre form stems from the engine.

It is a view he remains steadfast in, saying Ricciardo's comments during the Canadian Grand Prix weekend, in which he said the team isn't moving forward, were more the result of frustration given the contrast to his fortunes at the same race last season and the fact he was out-performed by Daniil Kvyat.

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Indeed, Ricciardo says the critical difference in the car still originates from the engine, adding that the car has made good progress since the start of the year.

"Our deficit I would say is 80-85% power unit and 15-20% chassis and there are some characteristics of the chassis that we are working on and will improve but it tends to become a vicious circle.

"I think there was a bit of frustration in his [Ricciardo's] comments, that he wasn't happy with his performance, that he had been out-qualified by his team-mate when expectation here, particularly after last year, were high.

"We have made progress with the chassis and we have brought development and improvement to the chassis really since Malaysia and at each grand prix, and we have a lot more in the pipeline throughout the year. I think we still have a weakness in the slow speed corners compared to last year's car and I think the nose regulation changes have affected us in that area, but I think the guys are getting a good grip on that now.

"Over the next few races we should see further steps with the chassis. The good thing is that, every two weeks, you can update the car and bring more performance to it whereas, with the engine, everything is a lot longer lead time."