The Impotence Association, which set up a help line for sufferers in 1995, has received calls from men aged 40-60 who have been told they cannot be treated.
"Some doctors are restricting treatment to younger men," said Dr Alan Riley, director of the sexual dysfunction clinic at St George's University Hospital, London and chief executive of the association.
While embarrassment deters many from seeking help, those who do often encounter difficulties. A survey for the association revealed half of those who consulted their GP found them unhelpful and in almost one in four cases the GP took no action.
Ann Craig, director of the association, said the helpline had received 18,000 calls in two years. Men reported being fobbed off and told to pull themselves together. One 54-year-old was told he couldn't expect to be "as active as a teenager". His wife left him two years later complaining that he didn't love her. Another was asked by his doctor: "What do you expect at 47?" A third said his GP told him it was "all in the mind".
An estimated three million men suffer from some form of erectile dysfunction, defined as a persistent failure to develop erections that are firm enough for sex. One in 10 men experience a sexual problem at some time in their life. Most who seek help from their GP are aged between 40 and 60 and in 80 per cent of cases there is a physical cause, suggesting an underlying medical problem - most commonly, high blood pressure, diabetes, heart disease and prostate problems.
Dr Riley said: "Many people believe that ED has a psychological basis, but the majority of cases are caused by physical changes. Most are treatable and it is unacceptable that men and their partners are suffering unnecessarily."
A variety of treatments are available, including injections direct into the penis which produce an erection, mechanical aids such as vacuum pumps, surgical implants and sex therapy. A non-injectable treatment, which involves inserting a capsule of drug into the urethra was launched last week.
However, a new US approach which is being hailed as - literally - a magic pill for ED, is the launch in the next few months of the first oral treatment .
The Impotence Association helpline is on 0181 767 7791.