Kimi Raikkonen, the only man standing between 24-year-old Alonso and the title, made an error in qualifying for the Brazilian Grand Prix. and starts on the third row in fifth place.
The German seized his second successive pole position as Williams swept champions Ferrari off the front row.
McLaren set the pace in Friday's Brazilian Grand Prix practice with Colombian Juan Pablo Montoya the fastest race driver.
World champion Michael Schumacher qualified fifth fastest for Sunday's Monaco Formula One Grand Prix.
Kimi Raikkonen went further, saying he had no intention of leaving McLaren.
India's Narain Karthikeyan will start 19th on the grid on Sunday's Turkish Grand Prix.
Fernando Alonso feels Sunday's inaugural Turkish Grand Prix could play to Renault's strengths.
Kimi Raikkonen will start Sunday's British Grand Prix from pole position after a flying qualifying lap that showed McLaren were back in business.
The McLaren driver suggested that whoever he signed for, it would be something of a gamble.
The International Automobile Federation (FIA) said in a statement that it was reviewing Sunday's race result after a timing discrepancy came to light.
The Spaniard will replace the Colombian at McLaren for the rest of the season.
The Finn, second in the Formula One championship to Renault's Fernando Alonso, suffered a blown engine in Friday's first free practice.
Team mate Sebastian Vettel was second fastest to complete the front-row sweep, with championship leader Lewis Hamilton third for Mercedes.
Ferrari's Michael Schumacher and Rubens Barrichello finished second and third respectively.
Germany's Nick Heidfeld was second for Williams with Australian team mate Mark Webber third for his first podium finish.
Renault's championship leader Fernando Alonso was pushed off the front row for his home Spanish Grand Prix.
Narain Karthikeyan finished 17th in the first qualifying round at the San Marino Grand Prix
Charles Leclerc seized the first pole position of his Formula One career on Saturday with Ferrari team mate Sebastian Vettel second fastest to lock out the front row for the Bahrain Grand Prix.
The Indian ace's Jordan-Toyota E15 developed electrical problems and he was forced to retire in the Bahrain Grand Prix.
Rediff's Formula One fanatics in a chat after the Melbourne Grand Prix.
The Flying Finn was clipped by Christian Klien's Red Bull and spun off the track
Formula One championship leader Nico Rosberg chalked up his seventh win in a row at the Russian Grand Prix on Sunday with team mate Lewis Hamilton fighting back from 10th on the grid to seal a Mercedes one-two finish.
