McLaren's racing director Eric Boullier has quit the team with Gil de Ferran appointed sporting director.

The team have reacted after a disappointing start to 2018 following their switch from Honda power to Renault.

Confirming Boullier's departure, team chief Zak Brown said the causes of McLaren's struggles "are systemic and structural, which require major change from within".

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As part of a radical restructure, former racing driver de Ferran will take up a new role of sporting director while Andrea Stella, who joined McLaren from Ferrari alongside Fernando Alonso, will be performance director.

Stella will be responsible for trackside operations with De Ferran tasked with maximising 'the effectiveness of the team's racing package'.

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In a statement, McLaren said: 'These changes are the beginning of a comprehensive programme of positive changes to the technical leadership of McLaren's racing organisation'.

McLaren are currently sixth in the Constructors' Championship with 44 points - 200 fewer than leaders Ferrari - despite the tenacious brilliance of star driver Alonso.

Boullier has been under increasing pressure following the team's failure to make a breakthrough towards the elite despite claims last year they possessed the best chassis on the grid but were being stymied by Honda's problems.

"I am very proud to have worked with such a brilliant team over the past four years, but I recognise now is the right time for me to step down," said the Frenchman.

Read more: McLaren explain problems with their 2018 car

Boullier leaves McLaren after four-and-a-half years at Woking and is the second significant management switch at the team so far this season.

Earlier this year, Tim Goss stepped down as the team's chief technical officer as the shortcomings of their MCL33 car become clear.

While Red Bull have won three races this term armed with the same Renault engine, McLaren failed to score in the three races before Sunday's Austrian GP when Alonso finished eighth.

"The performance of the MCL33 in 2018 has not met the expectations of anyone at McLaren, especially our loyal fans," acknowledged Brown.

Who is Gil de Ferran?

A former Indy 500 winner and two-time Champ Car champion, Gil de Ferran is a well-respected figure across motorsport.

The 50-year-old Brazilian enjoyed success on both sides of the Atlantic in his racing career, becoming champion in the junior British F3 championship in 1992 before achieving senior success at Indianapolis and elsewhere in American open-wheel racing.

After retiring from Champ Car in 2003, de Ferran worked in F1 for BAR/Honda as the team's sporting director between 2005 and 2007. He went on to experience racing stints in sportscars and a team owner in IndyCar.

In recent months, de Ferran has been working with McLaren as an advisor to help with the team's young drivers and provide expert assistance.

The Brazilian also has past experience of working with Alonso after helping coach the Spaniard in the intricacies of oval racing ahead of his Indy 500 debut last year.

Full statement from McLaren

'McLaren Racing Chief Executive Zak Brown yesterday accepted Eric Boullier's resignation from his position as Racing Director. He also announced a simplified technical leadership team.

'Simon Roberts, COO of McLaren Racing, will oversee production, engineering and logistics. Andrea Stella is appointed Performance Director, responsible for trackside operations. Gil de Ferran takes up the new role of Sporting Director, to maximise the effectiveness of the team's racing package.

'These changes are the beginning of a comprehensive programme of positive changes to the technical leadership of McLaren's racing organisation. The team will invest to retain and attract the best talent, internally and externally, to return McLaren Racing to the front of the grid.'

Zak Brown, CEO, McLaren Racing, said: "The performance of the MCL33 in 2018 has not met the expectations of anyone at McLaren, especially our loyal fans. This is not the fault of the hundreds of committed and hard-working men and women at McLaren.

"The causes are systemic and structural, which require major change from within. With today's announcement, we start to address those issues head on and take the first step on our road to recovery.

"I would like to take this opportunity on behalf of the entire team to thank Eric for his service and contribution to McLaren and wish him well in his future endeavours."

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