The supermarket Tesco says it is to start selling Viagra over the counter at the 'cheapest price'.

From next Monday, men with erectile dysfunction (ED) who don't have a GP prescription will be able to request the drug at 300 of its UK stores.

As the first supermarket to offer such a service, Tesco will charge £52 for eight of the blue pills. Boots pharmacy currently charges £55 for four.

Tesco stressed a pharmacist would make the sale and customers will be vetted.

Extra checks

The service is only available to men aged between 40 and 65 years.

They will have to complete a questionnaire and have their blood pressure and cholesterol measured, as well as undergo a test for diabetes.

Shona Scott, commercial manager for Tesco pharmacy services, said: "Provided that the men are suitable we will discuss their options and sell them an effective treatment."

Dr Nick Tomlinson of the Sexual Advice Association said offering over-the-counter treatments for erectile dysfunction could be a good idea.

"Men can be very embarrassed about going to their GP for help with things like this," he said

He added some men resorted to buying the drug over the internet, which could be risky because they might be sold fake Viagra.

Dr Tomlinson said it was essential that men seeking drugs for ED had thorough medical checks for underlying health problems.

"It's now realised that for a great many men, ED is a warning sign of cardiovascular problems that need checking out. Something like a third of men with ED go on to develop some sort of cardiovascular problem within five years."

He said men who see and get a prescription from their GP could purchase the drugs for even less - around £48 for eight tablets from some dispensaries.