McLaren's Lewis Hamilton posted the fastest time on the first day of practice for the Hungary Grand Prix.

The British driver was fourth quickest in a morning session led by of Ferrari duo Felipe Massa and Kimi Raikkonen.

But in the second session the overall leader in the drivers' championship was 0.248 seconds clear of Renault's Nelson Piquet Jr.

Hamilton, who is aiming for a third straight win, was nearly half a second quicker than Massa and Raikkonen.

The 23-year-old, who is coming off victories at the British and German Grands Prix, led the 20-car field with a best lap time across two 90-minute sessions on the 4.381-km (2.722-mile) Hungaroring track.

Piquet followed up his first podium at Hockenheim with the day's second fastest lap before skidding off the track to end his day.

Hamilton's team-mate Heikki Kovalainen, whose position with the British team for next season was confirmed on Thursday, was about two-tenths of a second behind in third.

Hamilton holds a four-point lead over his Massa in the drivers' championship.

After a poor performance in Germany Ferrari launched an investigation to determine what went wrong.

The team determined the car was not at fault but announced that their problems were a result of their drivers being unable to extract the maximum from the Bridgestone tyres.

They looked to have sorted out their problems in occupying the top two places in the first session, but were well off the pace in the afternoon run.

Britain's David Coulthard was 13th in his Red Bull, with Jenson Button - a winner here two years ago - down in 16th for Honda, just over 1.5 seconds behind compatriot Hamilton.

Sebastian Vettel endured a wretched day at the wheel of his Toro Rosso, propping up the timesheets on both occasions.

The young German completed just four laps in the morning due to a hydraulics issue and Vettel managed just five laps in the afternoon before again trundling off the track.

Practice wraps up on Saturday with a qualifying session to determine the starting order for Sunday's race.

Times from second practice session of the Hungarian Grand Prix:

1. Lewis Hamilton (GB) McLaren 1 min 20.554 secs
2. Nelson Piquet (Bra) Renault 1:20.748
3. Heikki Kovalainen (Fin) McLaren 1:20.760
4. Fernando Alonso (Spa) Renault 1:20.928
5. Kimi Raikkonen (Fin) Ferrari 1:21.009
6. Felipe Massa (Bra) Ferrari 1:21.010
7. Nick Heidfeld (Ger) BMW Sauber 1:21.138
8. Robert Kubica (Pol) BMW Sauber 1:21.363
9. Jarno Trulli (Ita) Toyota 1:21.505
10. Nico Rosberg (Ger) Williams - Toyota 1:21.581
11. Timo Glock (Ger) Toyota 1:21.662
12. Mark Webber (Aus) RedBull - Renault 1:21.733
13. David Coulthard (GB) RedBull - Renault 1:21.837
14. Kazuki Nakajima (Jpn) Williams - Toyota 1:21.902
15. Sebastien Bourdais (Fra) Toro Rosso - Ferrari 1:21.955
16. Jenson Button (GB) Honda 1:22.150
17. Giancarlo Fisichella (Ita) Force India - Ferrari 1:22.197
18. Adrian Sutil (Ger) Force India - Ferrari 1:22.358
19. Rubens Barrichello (Bra) Honda 1:22.448
20. Sebastian Vettel (Ger) Toro Rosso - Ferrari 1:22.945

Times from Friday's first practice session:

1. Felipe Massa (Bra) Ferrari one min 20.981 secs
2. Kimi Raikkonen (Fin) Ferrari 1:21.345
3. Heikki Kovalainen (Fin) McLaren 1:21.410
4. Lewis Hamilton (GB) McLaren 1:21.535
5. Fernando Alonso (Spa) Renault 1:21.802
6. Timo Glock (Ger) Toyota 1:21.931
7. Robert Kubica (Pol) BMW Sauber 1:22.267
8. Nelson Piquet (Bra) Renault 1:22.326
9. Nick Heidfeld (Ger) BMW Sauber 1:22.370
10. Jarno Trulli (Ita) Toyota 1:22.457
11. Mark Webber (Aus) RedBull - Renault 1:22.654
12. David Coulthard (GB) RedBull - Renault 1:22.700
13. Sebastien Bourdais (Fra) Toro Rosso - Ferrari 1:22.900
14. Jenson Button (GB) Honda 1:22.917
15. Rubens Barrichello (Bra) Honda 1:23.093
16. Nico Rosberg (Ger) Williams - Toyota 1:23.147
17. Kazuki Nakajima (Jpn) Williams - Toyota 1:23.274
18. Adrian Sutil (Ger) Force India - Ferrari 1:23.353
19. Giancarlo Fisichella (Ita) Force India - Ferrari 1:23.459
20. Sebastian Vettel (Ger) Toro Rosso - Ferrari 1:23.923