McLaren boss Eric Boullier says the team would be winning if they were still powered by Mercedes engines.

The Frenchman has also admitted the team will be powerless to stop Fernando Alonso leaving if they are not competitive in 2017.

McLaren gave up their supply of Mercedes engines three years ago to reunite with Honda in an exclusive partnership for the start of the sport's new turbo era.

Since then, McLaren-Honda have endured a painful struggle at the back of the grid but hit a new low in pre-season testing this year when they finished second bottom of the timesheets and recorded the fewest number of laps.

Asked directly at Barcelona by Spanish publication AS if he believed McLaren would be winners if they were armed with Mercedes power, Boullier replied: "I think we would."

Pressed whether he meant in 2017, Boullier reiterated: "Yes, we'd be winning again."

Honda problems are revealed

Speaking on the F1 Report - Testing Special, our guests think McLaren are a team in crisis following a disappointing display at testing in Barcelona. Speaking on the F1 Report - Testing Special, our guests think McLaren are a team in crisis following a disappointing display at testing in Barcelona.

Boullier's remarks follow the powerful condemnation of Honda by Alonso when the Spaniard launched a withering assessment of McLaren's form during testing.

"We have only one problem which is the power unit," said Alonso.

"There is no reliability and there is no power. We are 30kph down on the straight."

Alonso has already entered the final year of his McLaren contract and was contacted over the winter by Mercedes before the world champions signed Valtteri Bottas as replacement for the retiring Nico Rosberg.

"He wants to be competitive because he has talent to show the world and to himself," said Boullier of his star driver. "And we need to be competitive to keep him happy. If we're competitive he'll be happy and if not he'll take his own decisions."

How big are McLaren's problems?

From Sky F1's team-by-team review of testing...

'It continues to go from very bad to even worse for McLaren-Honda. After the pre-season proclamations of progress and the talk of using a clean slate of regulations to once again challenge the elite, Test Two somehow managed to exceed the expectations set by the first week. And in the most disastrous manner.

'Their best time of the week was a 1:21.348 from Stoffel Vandoorne, but looking at the timesheets doesn't do their 2017 struggles justice. They completed 159 laps less than any other team, but even that doesn't fully explain their current malaise. It is upon realising that their longest stint of the week - a paltry 11 laps - would only get the MCL32 roughly through a sixth of the Australian GP that you get a picture of just how far behind McLaren are. While their midfield rivals - it's far too early to start thinking about the top three - were comfortably completing race distances and more, McLaren were making the recovery truck an all-too-frequent visitor in the pits.

'Fernando Alonso put the blame solely on Honda's power unit, and that was before the MCL32 crawled to a halt on four different occasions over the final two days of pre-season testing. What's more, McLaren are believed to have made more engine changes over the two weeks than will be permitted over the duration of an entire season without penalty. "We have problems, clearly we have problems...but 'crisis' is a bit strong," insisted executive director Zak Brown. We'd hate to see a crisis if that's the case…'

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