Hamilton got a bit too close to the barriers in practice

He hit a barrier in the afternoon, after being delayed in the pits in the morning by mechanical problems.

"Everyone makes mistakes, and I'm only human - these small things happen," said the 22-year-old.

McLaren's Fernando Alonso dominated, finishing 0.6 seconds clear of Hamilton in the morning and 0.3secs ahead of Kimi Raikkonen in the afternoon.

Championship leader Hamilton completed just 14 laps in the morning and was forced to watch the second half of the session from the pit wall.

To compound matters, a piece of the starter-motor broke off and flew into the gearbox, which led to mechanics removing the floor of the McLaren to make repairs.

Hamilton was back on the track in the afternoon only to run into trouble 56 minutes in.

There is just no room for error in Monaco Lewis Hamilton

Hamilton lost control while braking for the first corner, the tricky Ste Devote right-hander and smashed into the tyre barrier.

He was quickly out of his car and clearly unharmed, if a little shaken, and was later seen waving to fans as he made his way back down the pit lane.

"I was pushing and right on the limit, which is something you always have to do at Monaco," said Hamilton.

"I then found the limit - at the mid-point of the second session - and found out how unforgiving this track can be.

"I just locked the rear wheels, and as it came before the apex, I lost the back end, tried to brake too quick, and went off into the wall.

"There is just no room for error in Monaco. To be honest, it was a light impact, even if it looked quite quick.

"I'm obviously sorry as there will be a bit of work for the guys."

606: DEBATE Hamilton is human after all HY

Hamilton insisted the error would have no bearing on the rest of his first race in Monaco, and McLaren boss Ron Dennis said he was not unduly worried by Hamilton's misjudgement.

"This is a mistake all drivers make of all standards. It's not something I will level any criticism at," said Dennis.

"I'd obviously rather not have a bent racing car but, under the circumstances, we're pretty comfortable with his contribution to this season.

"He still has a few Brownie points in hand."

Sainte Devote also caught out Britain's Anthony Davidson as he spun in his Super Aguri and nudged the tyre wall prior to Hamilton's shunt.

Although his incident lacked the impact of Hamilton's, it was enough to bring his session to an end, resulting in 19th place for the 28-year-old.

David Coulthard recovered from a spin through Loews hairpin that led to his Red Bull Racing car requiring a new rear wing to take 10th place.

Alonso, who trails Hamilton in the championship standings by two points, clocked a time of one minute 15.940 seconds for the 3.340km track.

Hamilton had to settle for third in the afternoon, completing only 19 laps in the second stint, and just 33 overall for the day - in contrast to many of his rivals who topped 60 plus.

Monaco Grand Prix, second practice:
1. Fernando Alonso (Spa) McLaren-Mercedes 1min 15.940sec
2. Kimi Raikkonen (Fin) Ferrari 1:16.215
3. Lewis Hamilton (GB) McLaren-Mercedes 1:16.296
4. Jarno Trulli (Ita) Toyota 1:16.354
5. Giancarlo Fisichella (Ita) Renault 1:16.753
6. Felipe Massa (Bra) Ferrari 1:16.784
7. Robert Kubica (Pol) BMW Sauber 1:16.848
8. Nico Rosberg (Ger) Williams-Toyota 1:16.852
9. Mark Webber (Aus) Red Bull 1:17.292
10. David Coulthard (GB) Red Bull-Renault 1:17.414
11. Rubens Barrichello (Bra) Honda 1:17.449
12. Jenson Button (GB) Honda 1:17.457
13. Takuma Sato (Jap) Super Aguri-Honda 1:17.459
14. Nick Heidfeld (Ger) BMW Sauber 1:17.486
15. Alexander Wurz (Aut) Williams-Toyota 1:17.516
16. Vitantonio Liuzzi (Ita) Toro Rosso-Ferrari 1:17.898
17. Heikki Kovalainen (Fin) Renault 1:18.086
18. Scott Speed (US) Toro Rosso-Ferrari 1:18.233
19. Anthony Davidson (GB) Super Aguri-Honda 1:18.328
20. Ralf Schumacher (Ger) Toyota 1:18.662
21. Christijan Albers (Ned) Spyker-Ferrari 1:18.820
22. Adrian Sutil (Ger) Spyker-Ferrari 1:19.358