The bill for paying interpreters has more than doubled in less than a decade, from £1.9million in 2006 to £4.9million in 2014.
Over the same period, the foreign-born population increased from 230,000 to 370,000, putting additional pressure on hospitals, GPs and other NHS services.
The national total, which also includes the cost of providing British Sign Language for deaf patients, works out at close to £14,000 per day.