The sudden abandonment of BHP Billiton's bid for Rio Tinto will push the former target's debt position even further into the spotlight, intensifying pressure on chief executive Tom Albanese to find a way through the world's frozen credit markets.

Rio's London-listed shares went into free fall last night after BHP pulled the pin on its offer, with the scrip losing as much as 45 per cent of its value in the hours after the news.