Former F1 driver Jos Verstappen says it would be a poor decision for Renault to retain the services of Russian driver Vitaly Petrov.

Although the announcement of Petrov as Robert Kubica's team-mate for 2011 is thought to be imminent, Verstappen has slammed the Russian as the "worst driver" on the grid.

"The Russian Vitaly Petrov I feel was the worst newcomer and the worst driver," Verstappen told De Telegraaf.

Although Petrov did have some bright moments, including keeping Fernando Alonso behind him in the Abu Dhabi Grand Prix, Verstappen thinks he has been far too inconsistent.

"Apart from this race I mostly see Petrov as good at making mistakes. Whether against a wall, spinning off or messing up his start, he ruined quite a few races and you can't let that happen when you're driving for a strong team like Renault.

"The different in quality and in points with his teammate Robert Kubica was enormous, but it's maybe not a fair comparison because Kubica - along with Vettel and Alonso - is the very best."

Petrov's inconsistency is also an area of concern for RenaultF1 majority shareholder Gerard Lopez, who said such areas need to be addressed if he is to improve.

"The one criticism we had of him and still have, to some extent, is not his pure speed but his ability to put together a whole weekend in a very focused and concentrated way," Lopez told ESPNF1. "If anything in Abu Dhabi, he showed that if he wants to, he can. There is no reason why Vitaly can't be a top five or six driver throughout his career but we haven't made a final decision.

"It's looking good but it's not going to be finalised until we sit down and get answers to the things we didn't like. If we're pleased with the answers, he'll be in the car next year."