Macquarie Bank, the Australian investment bank, is planning to take a new £1bn (€1.45bn) loan to refinance an existing £685m debt supporting its investment in the UK's M6 toll road.

Six banks are understood to have been shortlisted to underwrite the new nine-year loan with Banco Santander Central Hispano, BBVA, Calyon and Royal Bank of Scotland among them, according to bankers involved with the arrangement.