Mercedes deny favouring Nico Rosberg over Lewis Hamilton

Nico Rosberg has beaten Lewis Hamilton in every race since the Briton won his third world title last year

Mercedes have rejected accusations they are favouring Nico Rosberg over team-mate Lewis Hamilton this season.

In an open letter to fans posted on their website, the team address "the haters, the naysayers and the conspirators" following criticism on social media.

Mercedes also say it was a "miracle" Hamilton's car finished Sunday's Russian Grand Prix as the engine had zero water pressure for the last 16 laps.

They admit they have not met their own "expectations on reliability" in 2016.

The letter comes in the wake of four troubled races for Hamilton at the start of this season that have left him trailing Rosberg by 43 points - the equivalent of a win and a second place.

And the issues have left the world champion exposed to the likelihood of further difficulties later in the season.

The engine problems suffered by Hamilton mean he is likely to have to take grid penalties for using more than the permitted number of parts at some stage.

But the letter amounts to an impassioned plea to fans who have accused the team of trying to engineer a championship for Rosberg to reconsider.

"Performance-wise we are right on the money," the letter says, "but there is work to be done. Our goal is not simply to be fast but bulletproof, too. Not just to manage the problems but to understand them, fix them and ensure they are not repeated.

"We are working tirelessly to do just that and will continue to do so every step of the way.

"But there are no guarantees. This is a mechanical sport, balancing on the knife-edge of performance and endurance. You have to push the boundaries and failures can happen."

Mercedes say the entire team is "baffled and gutted" at the fact Hamilton has suffered identical failures in his engine's hybrid system in the past two qualifying sessions in China and Russia.

But they add they made a "monumental effort" to fly spare parts out to Russia overnight so Hamilton could start from 10th on the grid rather than the pit lane.

Lewis Hamilton has suffered a number of car problems this season

The letter explains in detail the engine problems both cars suffered in the race on the way to their one-two finish.

It says they saw "some alarming behaviour" from Rosberg's MGU-K - the part of the hybrid system that recovers energy from the rear axle - shortly after his pit stop.

"We spent a number of laps reassuring him he had a good gap over Lewis and could ease off before the FIA gave us the all-clear to tell him to switch to a setting that would control the issue".

Hamilton's water-pressure issue, they said, arose shortly after this at a time the Briton was setting fastest laps and closing on Rosberg.

"We needed to await confirmation from the FIA of what we could tell him over the radio (as a result of this season's restrictions on communication between team and driver)," the letter said.

It said that, with no water pressure for what amounted to nearly a quarter of the race, "the job he did to nurse the car home and still retain second place was truly remarkable", adding: "We genuinely aren't sure by what miracle the car limped across the line."