Enron, the ailing US energy trading group, has hired Blackstone, the US investment banking boutique known for debt restructuring advice, after the failed merger with rival Dynegy left Enron on the verge of bankruptcy.

Dynegy pulled out of talks with Enron on Wednesday despite having renegotiated the buying price to $4.91 a share from $10.98 a share. Dynegy said it was withdrawing following &quotEnron's breaches of representations, warranties, covenants and agreements in the merger agreement, including the material adverse change provision&quot.