By Alan Baldwin

MANAMA (Reuters) - McLaren will carry out a thorough investigation of their pitstop procedures after suffering costly holdups in Bahrain for the third successive race.

Jenson Button's hopes of victory in China last weekend were wrecked by a slow stop and it was team mate Lewis Hamilton's turn on Sunday with two agonizing delays.

The 2008 champion, who also lost time in Malaysia in the pits, ended the race in eighth place and lost the lead in the overall standings to Red Bull's winner and world champion Sebastian Vettel.

McLaren were also overtaken in the constructors' standings by Red Bull.

McLaren team principal Martin Whitmarsh told reporters that the same left rear wheelgun man was involved in both incidents, was distraught about it and had been relieved of his duties during the race.

Whitmarsh also said he had been to speak to him afterwards to tell him not to be too hard on himself.

"These are guys who don't get paid extra for doing it, they put themselves in the firing line, they put themselves under an enormous amount of pressure," he said.

"So naturally I am very protective of them, they deserve my protection."

Whitmarsh said McLaren would look now at the equipment, procedures and approach to prevent such incidents happening again.

He explained that Hamilton's first pitstop was slowed by the wheel nut pegs not engaging properly and the second because the nuts cross-threaded - the same as in Shanghai. All were on the same side and axle.

"We'll review lots of things but I don't think it's a criticism of him as an individual," said Whitmarsh. "He's taken it very badly and it's our job to support to him at the moment."

Button retired from the race, the fourth round of the season, after suffering a differential failure due to a cracked exhaust while chasing Mercedes' Nico Rosberg for fifth place.

Hamilton, who had started on the front row alongside Vettel and could have hoped for a top-four finish at least, said he would talk to the mechanic.

"I don't know who he is, but I will go and see the guy, try and lift him up," he said. "That's all I can do really, otherwise it's about doing my best and trying to remain positive.

"There should be (an enquiry) because we gave away a lot of points today which championships are lost through. So we have to try and make sure we pick up on them for the next race because we can't afford to lose points like we did today."

(Editing by Mark Meadows)