Macquarie Bank is moving closer to making a counter-bid for TBI, the UK airports group, subject to a £517m (€836.1m) hostile cash bid from Vinci, the French airports operator and construction group.

Macquarie Infrastructure Group, the investment arm of the Australian boutique investment bank, has intensified its due diligence enquiries into the state of TBI's business as it prepares to make a firm offer, according to sources close to the bidding process.