Jenson Button fastest for McLaren in opening Australian Grand Prix practice

Damp conditions early on meant relatively little serious running until the final half an hour, with Button going quickest by 0.245 seconds over team-mate Lewis Hamilton.

Michael Schumacher was third for Mercedes, followed by Fernando Alonso (Ferrari) and home hero Mark Webber (Red Bull).

World champion Sebastian Vettel was a quiet 11th in the second Red Bull.

Toro Rosso's Jean-Eric Vergne had the honour of leading the field out for the first time in an official session in 2012, and the Frenchman and team-mate Daniel Ricciardo had the track largely to themselves at first - choosing to rack up laps while the circuit was still drying, whereas most waited in the pits until conditions improved.

It was Ricciardo who duly logged the season's first flying lap with a 1m47.448s after 20 minutes.

Nearly an hour passed before the Albert Park circuit was in good enough shape for slick tyres. Sauber's Kamui Kobayashi - who by that time was the fastest man on intermediates - led the move to dry tyres and blew his previous benchmark away by just over five seconds.

Webber then deposed Kobayashi, who grabbed the top spot back again, but only momentarily before Schumacher began a long stint in first place, which lasted until Button put in his session-topping 1m27.560s with nine minutes to go.

Hamilton then joined his team-mate at the front with a lap 0.245s slower in the closing moments, pushing Schumacher back to third.

Alonso escaped a massive slide at the final corner on his last lap to take fourth, but his Ferrari team-mate Felipe Massa ended the morning in the gravel after putting a wheel on the grass under braking for Turn 9 with 13 minutes to go, sending the Brazilian spinning.

Nico Rosberg completed the top six for Mercedes, followed by Ricciardo, Pastor Maldonado's Williams, Kimi Raikkonen's Lotus and Kobayashi. Raikkonen only got out in the final few minutes after a long pause in the Lotus garage having his steering rack changed.

HRT endured what has become its traditional very tough start to an F1 season with neither car setting a flying lap. Pedro de la Rosa's machine was not ready in time to leave the pits during the session, while rising engine temperatures led to Narain Karthikeyan's car cutting out on the backstretch after 32 minutes.

Pos  Driver                Team                   Time               Laps
 1.  Jenson Button         McLaren-Mercedes       1m27.560s            11
 2.  Lewis Hamilton        McLaren-Mercedes       1m27.805s  + 0.245   14
 3.  Michael Schumacher    Mercedes               1m28.235s  + 0.675   17
 4.  Fernando Alonso       Ferrari                1m28.360s  + 0.800   21
 5.  Mark Webber           Red Bull-Renault       1m28.467s  + 0.907   21
 6.  Nico Rosberg          Mercedes               1m28.683s  + 1.123   22
 7.  Daniel Ricciardo      Toro Rosso-Ferrari     1m28.908s  + 1.348   23
 8.  Pastor Maldonado      Williams-Renault       1m29.415s  + 1.855   16
 9.  Kimi Raikkonen        Lotus-Renault          1m29.565s  + 2.005    8
10.  Kamui Kobayashi       Sauber-Ferrari         1m29.722s  + 2.162   26
11.  Sebastian Vettel      Red Bull-Renault       1m29.790s  + 2.230   21
12.  Nico Hulkenberg       Force India-Mercedes   1m29.865s  + 2.305   17
13.  Paul di Resta         Force India-Mercedes   1m29.881s  + 2.321   18
14.  Bruno Senna           Williams-Renault       1m29.953s  + 2.393   21
15.  Sergio Perez          Sauber-Ferrari         1m30.124s  + 2.564   22
16.  Romain Grosjean       Lotus-Renault          1m30.515s  + 2.955   16
17.  Heikki Kovalainen     Caterham-Renault       1m30.586s  + 3.026   16
18.  Felipe Massa          Ferrari                1m30.743s  + 3.183   11
19.  Jean-Eric Vergne      Toro Rosso-Ferrari     1m31.178s  + 3.618   17
20.  Vitaly Petrov         Caterham-Renault       1m31.983s  + 4.423    8
21.  Timo Glock            Marussia-Cosworth      1m34.730s  + 7.170    8
22.  Charles Pic           Marussia-Cosworth      1m40.256s  + 12.696  11
23.  Narain Karthikeyan    HRT-Cosworth           no time               3
24.  Pedro de la Rosa      HRT-Cosworth           no time               0

All Timing Unofficial