Mercedes team boss Toto Wolff made an extraordinary public apology to a crestfallen Lewis Hamilton on Sunday, describing his car as "undriveable" and unworthy for a world champion.

Wolff spoke on team radio and then to reporters after a desultory day for Hamilton, who finished the Emilia Romagna Grand Prix, in a lowly 13th while Mercedes team-mate George Russell was fourth.

Adding insult to injury, Hamilton was lapped by his recent nemesis world champion Max Verstappen.

Verstappen won the race ahead of Red Bull team-mate Sergio Perez to trim Charles Leclerc's lead in the title race to 27 points with Lando Norris finishing third for McLaren.

RELATED | Verstappen wins Emilia Romagna Grand Prix

Russell, 24, competing in the same difficult 'porpoising' and under-performing Mercedes car as the 37-year-old seven-time champion has now beaten Hamilton in each of the last three races.

"We are not good enough for a world champion -- and we just need to fix the car," said Wolff.

On team radio, he apologised to Hamilton as soon as the race ended.

"I am sorry for what you had to drive today. I know it was undriveable. This was a terrible race."

Hamilton responded: "No worries, Toto. Just keep working hard."

Hamilton's most humbling moment in a desultory race came when he was lapped by Verstappen, who enjoyed an easy pass for the race-leading Red Bull.

Sunday's result was one of Hamilton's worst since he joined Mercedes.

His only previous pointless finish came at last year's Azerbaijan Grand Prix where he was 15th.

His previous worst run of results came in 2009 when he struggled in an uncompetitive McLaren and registered his worst finish of 18th at the German Grand Prix.

Hamilton was at a loss.

"It's been difficult, but I don't really know what to say," he said.

"It's definitely not easy and we all feel it as a team. At least George got some points so my apologies to everyone (that) I wasn't able to do the same.

"I just wasn't fast enough to overtake and I don't really know why. I just wasn't moving forward. I was just a bit of a sitting duck."

Hamilton said he had experienced worse times in his career.

"I've definitely had lower moments so it's not the lowest, for sure," he said.

"Everyone's feeling it and everyone's just head down trying their best. There's no-one that's giving up and everyone's just trying to move it forward as fast as they can.

Mercedes is now third in the constructors standings with Russell having contributed 49 of its 77 points.

"Lewis is going to come back incredibly strong, I have no doubt," said Russell.

"He's definitely going to be pushing me all the way. I think it's just how things fall out sometimes in a race weekend. I made a very strong start -- I don't know what happened to him at the start.

"But I expect him to come back so strong. The way he is pushing and motivating the team is inspiring. I'm not getting comfortable with this position, because I know what he's capable of."