Burger King has developed a new customer feedback tool - and is encouraging its customers to participate by giving away free fries and drinks.

Guest Trac, developed by customer insight agency SMG, has been rolled out across 489 outlets in the UK and Ireland. It invites Whopper lovers to fill out a web-based survey by following the details printed on the back of their BK receipt.

Once they have completed the survey - which focuses on food quality, cleanliness and speed of service - they can print out a voucher for free fries and drinks.

Their responses will be fed back to Burger King in real time, which will then use the feedback to make improvements where necessary.