Manama: Daniel Riccardo's Renault F1 team boss Cyril Abiteboul says the problems which have led to two retirements in the first two races for the Australian driver are frustrating and unacceptable.
Ricciardo was in 10th position at the Bahrain grand prix on Sunday when he was forced to retire with a few laps to go.
"After a very intense winter, it's been a very bad start to our racing season," Abiteboul said in Bahrain on Sunday.
"Our race today came to a sudden stop so close to the finish.
"These problems are increasingly frustrating and unacceptable as both cars have shown very good competitiveness both over one-lap and race runs."
Ricciardo's retirement in Bahrain makes it two DNFs from two starts this season, after a premature end to his Australian GP.
The Bahrain GP, won by Mercedes' Lewis Hamilton, finished behind the safety car after both the Renaults, of Ricciardo and German teammate Nico Hulkenberg, stopped on track.
"A lot happened in the race today," Ricciardo said.
"Initially it looked like we had competitive pace and we therefore committed to a one-stop strategy.
"As we got deeper into the first stint, I could tell that the tyres were struggling a lot.
"In hindsight, two stops would have been better.
"Towards the end, the others were coming through, I couldn't do too much to defend.