A third of couples struggle to conceive

The survey, of 3,200 women with an average age of 37, found that 35% of couples struggle to conceive naturally. Previous studies put the figure at 14%.

On average couples spend £4,782 on fertility treatments. But less than half of women - 47% - go on to have a baby, according to a new nationwide fertility survey.

The researchers estimate that women currently between 30 and 45 will spend £1.7billion on private fertility treatments, including IVF, ovulation drugs, egg freezing and alternative therapies.

The study found that NHS trusts fully fund less than a quarter of couples seeking fertility treatment - leaving 77% to go private.

Reasons for female infertility included conditions affecting the womb and ovaries such as endometriosis and polycystic ovary syndrome, and blocked fallopian tubes - a problem that can be caused by the sexually transmitted infection chlamydia.

IVF expert Geeta Nargund said it was likely the figure of 35% of couples struggling to conceive was artificially high as the women questioned had not been given a firm definition of fertility problems. Traditionally, doctors use the phrase to describe couples who are still childless after a year of trying to conceive.

Dr Nargund, who is head of reproductive medicine at St George's Hospital in London, said that for many women, pregnancy late in life wasn't a choice but something they were forced into because of their working or financial circumstances.

She added: "We need to increase NHS funding. This research is a wake-up call to society and to government because it suggests a very small proportion of couples are able to get treatment on the NHS."