Independent retail chain Mills Group has ditched Challenge 21 for a Challenge 30 policy after twice getting caught out selling fireworks to underage shoppers in a Trading Standards sting.

The initiative has been rolled out to all 75 of its stores. The company has also spent £31,000 on employing an independent test-purchasing company.

"This is about eliminating any doubt for our staff," said Mills Group MD Nigel Mills. "There is little room for manoeuvre with a policy where everyone who looks under 30 is asked for ID."

The company had seen a dip in sales since the policy was brought in. Some shoppers thought it was "a bit harsh," admitted Mills. "We have lost some alcohol and tobacco sales and I'm not sure we'll necessarily get those customers back. However other shoppers who previously didn't shop here are now coming in."

There were no plans to drop the initiative despite the loss of sales, however. "This is a permanent policy for us. Despite our best efforts with Challenge 21 we still got caught by Trading Standards, so this is our way of protecting ourselves."

Reports from staff suggested they were getting less abuse from customers who were asked for ID under the scheme and fewer young people were coming in to try and buy booze.