Lewis Hamilton has stressed Mercedes cannot afford to stand still in the Formula 1 development race ahead of a possible four-way fight for the championship in 2018.

Hamilton wrapped up his fourth F1 drivers' title with two races to spare in 2017 despite a close fight with Ferrari's Sebastian Vettel for much of the season, while Mercedes clinched its own fourth consecutive constructors' crown one week earlier.

Mercedes' success made it the first team to defend its championships across a sizeable change in the technical regulations, but Hamilton is confident there is still room for improvement across the winter heading into 2018.

"It's been an amazing season, but by no means a perfect one. There are always areas you can improve on," Hamilton said.

"I won nine races and Valtteri [Bottas] won three, but there are 20 races, and a perfect season is when you win every single one of them. But it's a positive thing, because it means you can always improve.

"It was definitely one of the strongest seasons we've ever had. The beginning of the season was a little bit up and down, but the second part of the season was very consistent. Reliability has been the best it has ever been.

"In terms of my performance, my starts were much better this year, and I was much more comfortable with this year's car so that I was able to extract a lot more from it race by race."

Looking ahead to 2018, Hamilton said he feels as many as four teams could be fighting for top honours, tipping McLaren to fight back and join the battle at the front after switching to Renault power units.

"When I'm training and preparing for a new season, I firmly believe that we can be contenders for the next championship. It may turn out to be not possible, but you have to have that mindset," Hamilton said.

"If you go in with expectations of finishing fifth, it's not going to work. You've got to gear yourself up to win.

"Next year, McLaren will have Renault engines, then we may see four teams fighting for the championship.

"I think Red Bull will be quicker and Ferrari for sure will be fast again.

"We can't stand still - we have to keep moving forwards."