The Foxes Academy graduate, 20, heads to West London for the rest of the 2012/13 season, where he will hope to aid the Bees’ promotion push under former Manchester City striker Uwe Rosler.
Liam, who signed a new three-year contract with City in September, has made 14 appearances for the Foxes first team this term, most recently starting the 1-0 win at Burnley on 29 December.
He joins a Brentford side currently seventh in npower League 1, but with games in hand on several of the sides above them that should keep them firmly in the shake-up for automatic promotion.
The Bees’ next game sees them host Walsall at Griffin Park on Saturday – a game Liam could make his debut in, subject to his registration being confirmed by the Football League.