Tesco has joined forces with a London Primary Care Trust (PCT) to offer a free chlamydia-testing kit at a London store later this month.

The UK’s biggest retailer is working with Barnet PCT to deliver the pack in a Finchley store, although it is likely other PCTs will replicate the scheme.

It is the latest salvo from one of the big grocers, which are gunning to grab a larger slice of the lucrative retail pharmacy market from Alliance Boots and Lloydspharmacy.

Tesco is targeting customers aged between 16 and 25 years old, deemed by the Government to be most at risk from chlamydia. Those who contract the sexually transmitted disease often experience no symptoms, but it can cause infertility.

A Tesco spokesman said: “It was a request by the PCT and we are happy to help them with this.”

Alliance Boots introduced chlamydia testing at a large number of its stores in 2005 as part of a Government pilot.

In the past two years, Tesco has introduced a raft of new services, including smoking cessation and a personal health check. The grocer is understood to have enjoyed a strong take-up of its Tesco Health Check service, which launched this year. For£20, customers can have their body mass index, blood pressure, cholesterol and glucose levels checked, as well as a test for diabetes.

Separately, Sainsbury’s opened its first out-of-hours pharmacy at a store in Manchester last month and Asda plans to introduce a similar unit at two stores, in late spring.