Organ donations from hundreds of registered donors have been blocked over the past five years, figures show.

The data, which indicates that relatives blocked transplants in 547 cases since 2010, was released by NHS Blood and Transplant (NHSBT) to draw attention to the fact that family refusals mean people either wait longer for a transplant or die while on the list.

It estimated that 1,200 people missed out on a potentially life-saving transplant as a result of the refusals, which accounted for one in seven donations over the period.

NHSBT, which is responsible for the NHS organ donor register and for matching and allocating donor organs, said it was considering further steps it could take when approaching families to ensure more potential donors’ decisions were not vetoed.

One option would be to no longer ask the next of kin to confirm consent or authorisation. Their permission is not required by law if someone had registered a decision to donate on the NHS organ donor register.

Sally Johnson, director of organ donation and transplantation at NHSBT, said the body was already taking “a tougher approach – but also a more honest approach”.

“My nurses are speaking for the person who has died,” she told the BBC. “People who join the register want and expect to become organ donors. We do not want to let them down. We have every sympathy for families – and of course we do not want to make their grief worse. We think this will make what is a hugely distressing day easier for them, by reducing the burden on them.

“The principle that the individual affected is the one who consents applies throughout medicine, and it is not different because someone has died.”

NHSBT estimates that the blocked donors would have provided organs for 1,200 of the 6,578 patients on the waiting list for a transplant. Not asking relatives could result in the number of donors rising by 9%.

The exploration into how family “overrides” could be reduced comes after the number of people who donated organs fell for the first time in 11 years during 2014-15.

Other options being considered include providing families with a leaflet explaining that consent rests with the person who has died and not the family left behind. Such leaflets have already been produced by the Human Tissue Authority for Wales, Northern Ireland and England.

Another option would involve asking families to sign a document confirming their reasons for overriding their relative’s decision.

“This might help a family to discuss and consider their relative’s decision and hopefully honour it,” NHSBT said.

Families in Scotland are already required to complete a retraction form to record why they overturned a relative’s decision to donate. NHSBT said a similar form could be introduced across the UK.

Donations currently do not go ahead if a donor’s family feel that they cannot support donation, despite the donor registering their wishes on the NHS register.

NHSBT pointed to a survey it had carried out, which found that 73% of respondents said they thought next of kin should not be able to overrule someone’s decision to donate after they have died. The same survey found that 11% thought overrides were acceptable.

Sharon Brennan, who has spoken about how a transplant changed her life after she was born with cystic fibrosis, was among those calling for a more open discussion about organ donation.

Writing in the Guardian, she said that something had gone wrong with the way Britain was able to discuss organ donation and the spectre of death.

“I recently celebrated my 35th birthday, which I would never have reached if it wasn’t for my donor,” she said. “But in these cases of overridden consent, I feel most sympathy for the 547 people who were denied the opportunity to leave this Earth in the way they had planned.

“If we could openly discuss donation without feeling squeamish and upset, then perhaps we would feel less distraught if faced with a decision about organ donation, less likely to dissent and more able as a society to feel comfortable enforcing the law around individual consent.”