Almost a fifth of those questioned said their GP never referred them.

The poll was carried out at the Teenage Cancer Trust's national conference taking place this weekend in Nottinghamshire.

More than 350 young people who have had, or currently have, cancer attended - a number of whom expressed concern about how long it took them to be diagnosed.

While 26% of the 356 delegates who had or have cancer paid their GP four or more visits before getting a referral, a further 13% said it took them three visits before they were given an appointment with a specialist.

However, more than a fifth (21%) said they only had to see their GP once before being referred.

One former leukaemia patient, 21-year-old student Zara Sree, from Telford, Shropshire, said she saw her GP about 24 times during a 12-month period before she was referred to a specialist. She said: "I was going back and forth to my GP for about a year with symptoms like tiredness, bruising, loss of appetite and recurrent infections.

"The symptoms were put down to anaemia and being generally unwell. I was then referred to a hospital, where I had blood tests every month, but they didn't pick up the leukaemia for another six months."

After six months of chemotherapy and a bone marrow transplant, Ms Sree has now been in remission for five years, but said the time it took her to be diagnosed was too long.

However Professor Steve Field, chairman of the Royal College of General Practitioners, said it was difficult for GPs to diagnose cancer in teenagers because it was so rare. He said: "Many of the signs and symptoms that teenagers have are common to other, non-serious illnesses. The College has been trying to raise awareness of teenage cancer and of cancer generally, but it's very difficult because of the rarity."