Australian Oscar Piastri said a “breakdown in trust” with Alpine led to his decision to reject them and join McLaren for his debut next season.

“McLaren was a great opportunity. They were very straightforward and very keen to have me,” Piastri said.

“There was a lack of clarity around my future at the team at Alpine.”

Piastri’s comments echoed those of Fernando Alonso, Alpine’s race driver this year, who also described a lack of “trust” from the team when explaining his decision to join Aston Martin in 2023.

The two-champion had previously said his “priority” was to stay with Alpine. But they were offering only a one-year deal when he wanted a longer-term contract, and negotiations reached an impasse.

After being taken by surprise by Alonso’s announcement that he was moving to Aston, which came the morning after the Hungarian Grand Prix at the beginning of August, Alpine’s management took a series of apparently ill-advised actions in a vain attempt to keep hold of Piastri, their reserve driver and reigning Formula 2 champion.

Their team principal Otmar Szafnauer held a news conference in which he claimed the team were confident of their contractual position with Piastri, and then later that day issued a statement announcing that he would drive for them next season.

Shortly afterwards, Piastri announced on Twitter that that was not the case, and he would not be.

Piastri, who was talking to the Formula 1 website, said his manager Mark Webber had twice informed Alpine that he would be leaving, adding that the team’s actions were “quite upsetting as the announcement was false and it also denied me the opportunity to properly say goodbye to everyone at Enstone [Alpine’s UK base in Oxfordshire].”

The CRB ruled that Alpine had no valid contract with Piastri for 2023 and beyond.

The case has cost Alpine a total of nearly £540,000 in legal fees, including being required to pay McLaren’s costs.

Piastri said: “[Alpine] publicly stated they wished to continue with Fernando for at least one or two more years. I respect that.

“But after spending the year out, my hopes were firmly set on an Alpine seat. And the lack of clarity and, similarly to Fernando, a bit of a strange feeling in negotiations, it didn’t feel like it was the right decision for me [to stay around].

“The lack of clarity around my future, and ultimately a breakdown in trust, I felt the very attractive offer of McLaren and the positive dealings with them thus far were all reasons why I felt McLaren was where I was best off for the future.”

The CRB revealed that Piastri signed for McLaren on 4 July. The team then negotiated a release with Daniel Ricciardo, terminating his contract a year early, to make way for Piastri.

Szafnauer has twice described a conversation with Piastri before Alpine put out their announcement, saying he went to see the driver in the simulator at Enstone to tell him that they were going to announce he was joining them in 2023. Piastri, Szafnauer said, smiled and thanked him.

Piastri said: “That was a bizarre and frankly upsetting episode. It was done publicly in front of some members of the team who were oblivious to the situation and I didn’t want to cause a scene in front of them.

“Once we were in private, I told Otmar what our position was and what he had been told multiple times before that. It was very surprising to me to make that announcement.”

Szafnauer did not mention the second part of the conversation detailed by Piastri.

McLaren team principal Andreas Seidl added: “Alpine was informed well in advance before the announcement they made regarding Oscar driving for them next year. Informed by Oscar, including conversations Zak [Brown, the McLaren Racing chief executive officer] and myself had with the management Alpine of what was going on.”

Alpine have yet to explain why they pursued the case with the CRB despite lacking a valid contract and having been told by both Piastri and McLaren that the driver was leaving.

Szafanuer said: “The right thing to do is to have a have a look at what happened, understand where the shortcomings were and fix them for the future.”

Seidl said: “The reason why I wanted to get Oscar on board is because he has shown in his junior career that he is a very talented driver with a lot of potential. I think also in terms of personality he has everything he needs in order to be successful in Formula 1.

“He is young, fresh, full of energy. I think he has the right level of self-confidence as well. But at the same time he’s very humble and he’s fully aware of the big challenge that is ahead of him.

“It is complex for any rookie to join Formula 1. But I feel with the team we have in place, with everything Oscar has, that we are in a very good place in order to get him well prepared before he starts his first race next year in Bahrain.

“I’m quite optimistic that he can first of all have a good start with us and then have a great career.”