Fernando Alonso has backed Lewis Hamilton's decision to leave McLaren and switch to Mercedes and said he expects the Briton to be a championship contender straight away with his new team.

Hamilton confirmed last Friday that he was to end his 14-year relationship with McLaren and take on a fresh challenge having been named as the replacement for Michael Schumacher in the Mercedes line-up.

Alonso himself partnered Hamilton in his debut season in F1 back in 2007 before leaving to return to Renault after a single year but he said it was no bad thing that his former team-mate had moved to pastures new.

"I think it's normal, it's just steps on your career," the Spaniard said. "I said when the rumours were there that for Lewis it's a good thing to move on.

"From McLaren, Prost moved on, then it was me, now it's Lewis. Normally for a better life. A good change."

Alonso said he was sure that Hamilton would be a success in his new team and would be strong from the outset when he makes the switch for 2013.

"I think he did great in McLaren," he said. "He won one world championship...he won races, he is considered one of the best drivers and next year I think he will enjoy more and be very competitive.

"From next year I think he is a clear contender for the championship with Mercedes. They are a top team and with Ross Brawn there and all the potential of a big company behind they are very strong."