Mercedes chairman Niki Lauda has given some insight into the tense relationship between Nico Rosberg and Lewis Hamilton last season.

The 2016 Formula One world championship was their last as teammates and the first in which Rosberg came out on top, retiring as world champion at the end of the season. The title battle went down to the last lap of the last race, with Hamilton keeping the fight going until the chequered flag by backing his teammate into rival drivers as they ran one-two at the front of the field.

The tension between Rosberg and Hamilton was clear throughout their period as teammates, but in an interview with Graham Bensinger on YouTube, Lauda opened up on the depth of the feud.

"They had no relation, which is always bad," Lauda told Bensinger. "They were so bad that they didn't even say hello in the morning. I don't expect them to have breakfast together if they don't like each other, I don't expect them to sit down and have breakfast, but the relationship was really bad. It affected Lewis mainly and Nico [as well], so it was fine but not easy."

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A collision between Hamilton and Rosberg at the 2016 Spanish Grand Prix proved to be a major flashpoint in their relationship. In the immediate aftermath, Mercedes' management summoned both drivers to a meeting in the team's engineering trucks where Lauda made it clear that he thought Hamilton was to blame.

"The big question was whose fault was it?" Lauda said. "For me it was clear because Lewis was too aggressive going to the right, hit the grass, couldn't stop his car and then hit him off.

"I said if I have to choose between the two it's more Lewis' fault than Nico's fault. And Lewis did not appreciate that, because he was of a different opinion. He said, 'Why do you criticize me?' I said, 'Excuse me. I cannot accept that you guys crash and then we have nothing and nobody's fault. For me it has to be somebody's fault.' And then Lewis really got upset. Nico said, 'Yes, it was your part too, you moved to the inside. Why did you not leave room?' He said, 'Why should I, I was doing the race'."

Lauda said he met with Hamilton again in Ibiza to talk through the incident one-on-one, while Mercedes issued a stricter set of rules of engagement to its drivers. Lauda said the rules came with the ultimate threat of a driver being released from his contract if he did not act in the interests of the team.

Lewis Hamilton and Nico Rosberg endured a strained relationship as teammates at Mercedes. Mark Thompson/Getty Images

"We put some regulations in, we told them -- especially in Barcelona when the pushed each other off the track -- we said this was unacceptable for Mercedes and one of you guys has to win [the race] you cannot push each other off.

"We had some rules put in, that you are not allowed to [do that] and you have to pay a penalty if you do it again or we will think of releasing you from your contract, because we are team players here and we cannot destroy each other. This was the thing. Toto came up with some good rules and we had peace again. We fought hard and the accidents got reduced between them."