Intensive care doctors have told the BBC they are deeply concerned about any radical change to the law on organ donation.
Prime Minister Gordon Brown has called for a change to an opt out system called presumed consent.
A UK-wide government taskforce is due to report in the next few months.
A poll of adults across the UK for the BBC shows two thirds of the public now support the idea - but intensive care doctors are more divided.
The Intensive Care Society says its research suggests many specialists are worried such a move could damage the trust between patients, their families and doctors.
Kevin Gunning, a consultant at Addenbrooke's hospital in Cambridge, has carried out a survey of specialists for the society.
The 125 responses from doctors around the UK shows opinion divided almost down the middle.
Some doctors are concerned presumed consent might instil doubts in patients and relatives about a potential conflict of interest.
Mr Gunning said: "In intensive care patients are often admitted suddenly and the families have to comes to terms very quickly with the fact that someone may not survive.
"It is very important in this situation that we have their trust, that we are doing is going to be in the best interests of that patient."
While he strongly supports the principle of organ donation, he believes any consideration of presumed consent is premature.
"The trouble is we live in a society where people are very much worried about the interference of the state.
"I think you would find that families would view this as taking the organs - and that would create a tension."
Around 30% of patients admitted to intensive care die before leaving hospital.
Their deaths have the potential to benefit patients on the transplant waiting list.
Long waiting lists
The UK has a low rate of organ donation compared to some European countries.
There are just over 7,000 people currently on the active waiting list, and that number is growing by around 8% each year.
Every year almost 1,000 people die either while on the list, or having become so ill they are no longer able to withstand transplant surgery.
Rod Lenette is one of the many whose lives are on hold while they wait.
Now 41, has spent more than four years on dialysis, making an hour long trip each way to the unit at Addenbrookes.
"The problem is when you are on this machine you can't see beyond it," he said.
"I would be a proper dad to my children - I'd be a proper husband to my wife.
"I used to be the cornerstone of my family I kept everyone together and I haven't been able to do that."
The British Medical Association and the Royal College of Nursing have both backed the idea of presumed consent.
And an ICM poll for the BBC of adults across the UK reveals 66% now support presumed consent.
In January the government appointed taskforce proposed an overhaul of the organ donation system in the UK which all the health departments are committed to implementing.
Many believe those changes should be given a chance to make a difference before any change to the law is considered.
Opinion is even divided among donor families, reflecting the often intensely personal nature of views around organ donation for transplant.
Barry and Elizabeth Jenkins have lived through making an organ donation decision.
Their son Richard was at home when pins and needles took him to the family doctor for a check up.
Just 17 days later Richard was dead at the age of 24 from a rare brain tumour and his parents agreed to donate his kidneys and corneas.
They waited for him to die in a room next to the operating theatre to allow organ retrieval.
Both Barry and Elizabeth are passionately in favour of organ donation but just as strongly opposed to presumed consent.
Mr Jenkins said presumed consent would damage the delicate relationship between the donor, the donor's family and the doctor.
He admitted he had doubts about the issue before agreeing to it in his son's case, adding: "With presumed consent they would be greater."
Mrs Jenkins said: "It's not just whoever's put their name down on the register, it's a discussion with the family who are going to be left afterwards."
The taskforce has run focus groups to explore some of the complex issues around presumed consent before writing its report.
They may well have revealed some of the wide range of views this debate can provoke.
Without a strong consensus they may find it difficult to conclude that changing the law is the most urgent priority in improving the rate of organ donation in the UK.