Last updated on .From the section Formula 1

Mercedes drivers Valtteri Bottas and Lewis Hamilton set the two fastest times in testing in Barcelona

Mercedes say their new Formula 1 car is "a big step forward" compared with its world championship-winning predecessor.

Technical director James Allison said they would start the season next month with improvements to the aerodynamics and engine.

The team had "a good winter" and produced a series of innovations to try to fend off challenges from rivals, he added.

"We decided we would make a car that was aggressive," he said.

"Take every part and challenge ourselves to make it better."

Allison used a video produced by Mercedes external-link to detail three main areas of innovation on the car - but did not touch on the new 'dual-axis steering' system that surprised their rivals at last week's first pre-season test.

Allison said: "The challenge was, in a year where the regulations are completely stable and where the tyres haven't changed one little bit, how do we take last year's best car, the 2019 Mercedes car, and produce something properly competitive when the regulations haven't changed?

"The temptation for us was just to keep polishing that one - after all it finished the season really strongly and it was developing very fast all the way through the year, so there was still lots of opportunity to make that one quicker.

"That conservative approach was very, very tempting. But in the end, we decided that wouldn't be enough."

He detailed three main areas of progress:

Changes to the front suspension and wheel assembly to give "more aerodynamic opportunity in the front end", which had produced "good aerodynamic gains"

An upgraded engine that has "a really impressive upgrade in power" and can also run cooler to allow the team to make the radiators smaller and the car more tightly packaged for better aerodynamics

An "extremely adventurous" rear suspension redesign, which has also allowed the team to create more downforce

He said the front and rear suspension changes had been "a structural compromise" that had added weight, but that this had been offset by changes elsewhere.

Allison said: "We have got a car here whose development slope has kicked up, is steeper than the one we finished last year with, in that very, very good car from 2019, and we've got a car that we hope will be fertile ground to develop strongly all the way through the 2020 season."

Mercedes are aiming for a seventh consecutive drivers' and constructors' championship double this year, having set a new record of six in a row in 2019.

And driver Lewis Hamilton hopes to win a seventh world title, which would put him level with all-time record holder Michael Schumacher.

Mercedes drivers Valtteri Bottas and Hamilton set the fastest times at last week's test. The second and final pre-season test runs from 26-28 February, and the first race is in Melbourne, Australia, on 13-15 March.