The NHS advises that women's fertility starts to decline sharply from 35 and those planning to have a family should take this into account.
But Lord Winston, who heads the Genesis Research Trust in London, dismissed this. He said women are able to conceive until their mid-40s and suggested fertility clinics that say otherwise are doing so for financial gain.
Speaking on Good Morning Britain on Wednesday he said: 'Actually even at the age of 40 your chances of getting pregnant spontaneously are pretty good if you keep trying, and it's really not until you're 45 there is a really sharp turn off.'
His view is in stark contrast to the NHS Choices website, which says: 'In women, fertility declines more quickly with age. This decline becomes rapid after the age of 35, particularly due to the decline in the quality of the eggs released by the ovaries.'