Adrian Newey feels F1 needs to increase the emphasis on the role of the chassis, claiming that differences in performance have become too reliant on the engine.

Speaking ahead of the 2015 season, Newey was discussing the improvements Red Bull have worked on over the winter to help it get back on terms with Mercedes after ceding its world title to the manufacturer in 2014.

However, Newey admits there are only so many developments Red Bull can make to the chassis due to the rigid regulations, thus placing greater emphasis on the Renault engine, a power unit that was maligned for its speed deficiency and reliability compared with its Mercedes counterpart.

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As such, emphasis has been placed on bringing the power unit up to speed, but having identified a '10 per cent' deficit to Mercedes, Newey admits it is difficult to expect Renault to bridge that gap in the short-term.

"I think Renault has now accepted, or stated, that the power deficit was around ten per cent, which was our estimation from our own analysis. Obviously they've come to their own opinion but it's a big number and really, for Renault, it's not something that's easy for them to overcome in a very short period of time.

"I think they've done a very good job of developing the engine over the winter but you don't overcome a ten per cent deficit in a few months and that's the position we're in at the moment - better than last year but still considerably down on where we know Mercedes were last year and that's obviously not taking into account the findings they've had over the winter.

"That's the nature of the engine business - it's a much longer lead time, with slower development curves than the chassis manufacturer, because the parts take so much longer to manufacture.

Indeed, Newey believes the regulations place too much emphasis on the power units, making it difficult to make gains on chassis tweaks alone.

"This year, for us, it's going to quite difficult and I think that's where things have got a little out of kilter. In my opinion, F1 should be a blend of the performance of the driver, the chassis and the engine, and I think the current regulations have swung too much in favour of the engine with a very restrictive set of regulations on the chassis, so if an engine manufacturer derives a benefit it's difficult for a chassis manufacturer to make enough of a difference to overturn that.

"Clearly there are differences between chassis and, as we saw last year, I'm not entirely sure that all the Mercedes cars had exactly the same engines in them when it came to software and fuel but certainly the Renault cars did. I can't comment on the Ferrari cars and there was a difference in performance between the Renault powered cars. It's not to say that there isn't a difference in performance between chassis, of course there is, but it's more difficult to find that last little bit."