The Competition Authority raided a number of Portugal’s largest banks as part of an inquiry into allegations of interest and mortgage rate-fixing.

The operation, which was three weeks in the planning, came after the Authority received information suggesting banks had shared sensitive data. The banks raided have denied sharing data, which would be in breach of antitrust laws.

If the banks are found to have breached these regulations, they face fines of up to 10 per cent of their annual turnover.