Robert Kubica's sponsor says Williams broke "certain provisions" of its contract in 2019.

It is now certain that PKN Orlen, the Polish oil company, will leave Williams along with Kubica after the forthcoming 2019 finale in Abu Dhabi.

"Robert was quite critical of the organisation and preparation of the team after each grand prix and it's hard to disagree," said Adam Burak, Orlen's communications boss.

"We assume that certain provisions of the contract were broken by withdrawing Kubica in order to save parts in Russia," he added.

"We are in dialogue with Williams but we are convinced that we are right."

As for Kubica and Orlen's next move, Burak said the company is determined to stay in F1.

"As a brand we are now more recognisable which is why we have decided to stay in F1 after parting with Williams," he told Sportowe Fakty newspaper.

"Shortly after Abu Dhabi we will be able to talk about the details."

Orlen's 2020 backing has been linked with several F1 teams, including Haas, Racing Point and even McLaren.

Kubica, meanwhile, could combine a F1 reserve role with a race seat outside of the paddock.

"We have several scenarios on the table," said Burak. "You can be with a team or be associated with the whole of Formula 1.

"For us, this year was a business success, just not in sporting terms. But as a commercial company, we are guided by business.

"For Robert, he is a free man. We know and accept his expectations and he wants to race," Burak added.

"We would like to stay with Robert as one of the most recognisable athletes, so we must be flexible."