Dr Allan Pacey, a senior lecturer at Sheffield University Medical School, said a national shortage of sperm donations was leading couples to take desperate action to have a baby.
He warned that women are buying sperm online to carry out DIY insemination, which is fraught with risks.
Other women are travelling overseas for treatment, sometimes paying large amounts.
Dr Pacey, writing in The Obstetrician & Gynaecologist (TOG), said: "We are really in a terrible position in the UK with regard to the provision of sperm donor assisted conception."
He said latest figures from the Human Fertilisation and Embryology Authority (HFEA) showed 1,779 patients in 2007 received treatment with donor sperm – the lowest number ever.
This was in part because patients were opting to receive other treatments, he said, but added: "It is almost certainly as a consequence of a serious shortfall in the number of sperm donors available."
A previous audit showed 85 per cent of applicants of sperm donation were rejected because of poor semen quality. Of the remainder, the sperm of only 3.6 per cent of the accepted applicants was used in assisted conception, after further screening.
Susan Seenan, from the support group Infertility Network UK in Scotland, said people were spending more than three years on waiting lists, forcing them to consider other ways to get hold of sperm, such as using the internet.
She said: "The desire to have a baby can be such an overwhelming and deep-rooted desire that they may go to lengths that other people might not understand.
"If that's the only way they can access treatment then some people will be driven to it."
She said some people going abroad had very good experiences, but she did not think they should be forced to go due to shortages at home.
And she warned that there were huge risks involved with using sperm from the internet – which may not have been through safeguards or tests.
Ms Seenan believes the problem stems from a change in the law in 2006, which resulted in the removal of donor anonymity.
Individuals conceived through donor insemination now have the right to know who their genetic father is at the age of 18.
She said: "At that stage we started to see a drop off in the number of donors coming forward. There is no financial responsibility but some people are put off by it."
She added: "We would like to see more and more people being aware of the problem and that they could possibly help."
Jason Waugh, TOG editor-in-chief, said the "crisis in donations" needed to be addressed. Otherwise, he warned "women will be driven to seek sperm from sources that may be unregulated and questionable".