Context :

Aims : We look for wide , faint companions around members of the 5 Myr Lambda Orionis open cluster .

Methods : We used optical , near-infrared , and Spitzer/IRAC photometry .

Results : We report the discovery of a very wide very low mass visual binary , LOri167 , formed by a brown dwarf and a planetary-mass candidate located at 5 arcsec , which seems to belong to the cluster .
We derive T _ { eff } of 2125 and 1750 K. If they are members , comparisons with theoretical models indicate masses of 17 ^ { +3 } _ { -2 } and 8 ^ { +5 } _ { -1 } M _ { jup } , with a projected separation of 2000 AU .

Conclusions : Such a binary system would be difficult to explain in most models , particularly those where substellar objects form in the disks surrounding higher mass stars .