Women trying to get pregnant blame a man's tight underwear for their low sperm count, a study found.

But they blamed his high stress levels, drinking, smoking or taking recreational drugs for reducing his chances of conceiving.

While women reach for the vitamin supplements to boost their fertility but men are more likely to hit the gym to get fit, lose weight and sleep and relax more, a new survey found.

Both sexes were equal in dumping the junk food, quitting smoking, drinking and reducing their caffeine hits in a bid to start a family.

But 50 per cent more men thought their sacrifices would have more of an affect on their fertility than changes made by their partner on her fertility.

Women also said their man's high quality diet, physical fitness, vitamin or food supplements pills and youth were positive factors for improving his chances to conceive.

And nearly half - 47 per cent - of women surveyed blamed a man's tight underwear for damages his sperm.

The Fertility5050 survey was funded by FutureYou, a Cambridge-based supplement company which is launching a male dietary supplement called Fertility+ to boost sperm quality.

The national survey of 2,052 men and women under 44 explored the difficulties couples had in trying for a baby.

It comes as sperm counts plummet across the western world at the same time men are leaving it later than previous generations to become a father.

The survey found just under a third of women said they took vitamin supplements compared to just over a sixth, 17 per cent, of men.

But 14 per cent of men would lose weight or increase their fitness compared to just eight and six per cent respectively of women.

When it came to identifying things that had a positive impact on a man's fertility three fifths of women identified a high quality diet, half their man being highly physically fit, a third taking food supplements or vitamins and a third their youth.

But nearly seven in ten blamed drinking, drugs and smoking while six in ten blamed stress for their man being a flop.

The dietary supplement is based based on a new molecule called LactoLycopene and Dr Alf Lindberg, a medical advisor to FutureYou, said: "We are anxious to encourage greater interest in male fertility problems.

“There is now a great deal of evidence to support the use of this compound, but more work is needed to establish which men will benefit the most, and to prove that the improvement in sperm quality leads to greater numbers of live births."

Lactose, a milk protein has been shown to improve the absorption of lycopene - a nutrient found in tomatoes that has been shown to improve sperm quality in subfertile men.

Cambridge Nutraceuticals, the parent company of the FutureYou brand, is testing the efficacy of Fertility+ in a research project at the University of Sheffield.

Liz Williams a Senior Lecturer in Human Nutrition at the University of Sheffield said: "This survey highlights the pressures felt by both men and women trying to conceive and the strain that fertility issues can place on relationships.

"It is important that these issues are discussed and that men have the same access to advice and support as women. "It is also important that we explore lifestyle strategies, including nutrition, to enhance a couple's chance of successful conception."

Results which are believed to have been positive are expected to be published later this year.

The new supplement comes as the fertility treatments have focused on the men.

Until now the test tube baby industry has been dominated by gynaecologists who have been accused of channelling couples straight into IVF without investigating men’s health beyond a basic test to see if they are producing live sperm.

Now men’s problems are moving into the spotlight.

Consultant urologist Jonathan Ramsay of Imperial College NHS Trust and Hammersmith Hospital said: "It is great to see so many men taking responsibility for their reproduction.

"If all men were investigated prior to commencing IVF treatment we could see a significant rise in the current success rate which is under 25 per cent.

“It is an absolute scandal that more hasn’t been done about this.

“Half the time if a couple has fertility problems it is due to the man, but they are never properly investigated.

"There is increasing evidence that one in three infertile men have DNA damage to their sperm probably caused by poor diet and lifestyle, and that can be treated.

“Women are now encouraged to take folic acid to improve the quality of their eggs and reduce neural tube defects in babies.

"I see no reason why we shouldn’t develop a similar treatment to improve reproductive health in men.”

Aileen Feeney Chief Exec of Fertility UK said: "Men are half of the fertility equation, when they cannot create the family they long for without medical help they suffer and struggle physically and mentally just as women do."