Health Secretary Andy Burnham said today he deeply regretted the distress caused to bereaved families of people whose organs were removed without consent following a huge blunder affecting the UK donor register.

Around 800,000 people had their wishes about the use of their organs wrongly recorded due to an error, it was revealed yesterday.

An investigation found that 45 individuals for whom false data were stored have since died.

The NHS is about to contact approximately 20 families who allowed organs to be taken after being misinformed about what consent had previously been given.

Mr Burnham said: "Giving the gift of an organ is a most selfless act and organ donors transform the lives of thousands of people every year.

"I want to assure the millions of people on the organ donor register that they can have full confidence that only their accurate information will be discussed with their families, and that their wishes will be respected.

"This has clearly not happened in a small number of cases in the past, and I deeply regret the distress caused to the families.

"In all cases, donation was discussed with family members before decisions were made. It is important that those who wish to donate tell their families of their wishes."

He added: "I have asked NHS Blood and Transplant to take immediate steps to identify and contact all affected families. This process is under way and will be completed as quickly as possible.

"I have asked Professor Sir Gordon Duff of Sheffield University to carry out a review to find out why this has happened, prevent mistakes like this being made again and ensure all necessary steps are taken to maintain confidence in the organ donor register."

Joyce Robins, of pressure group Patient Concern, told the Sunday Telegraph: "This Government has got an absolutely dreadful record when it comes to data, but it is absolutely horrific that such sensitive details were handled in such a careless way."

Donors can give permission for any of their organs to be taken, or provide more specific agreements.

Many donors have strong views about what can be taken. Often consent is not given for eyes to be removed, or bodies to be used in medical research.

But the distinctions were accidentally deleted in 1999, when details held by the Driver and Vehicle Licensing Agency - which includes a request for consent in applications for a driving licence - was transferred to the organ registry.

The mistake came to light last year when NHS Blood and Transplant wrote letters to new donors thanking them for joining the register, and outlining what they had agreed to donate.

Respondents wrote back complaining that the information was wrong.

After detecting the error, NHS Blood and Transplant, which runs the organ donation register, was able to correct 400,000 of the flawed records.

But hundreds of thousands more people are due to be contacted shortly and asked to confirm what consent was given.

Until fresh consent is obtained, organs will not be taken from any of those people in the event of death.

It is illegal to remove organs without prior consent from the person who died, or their next of kin.

In the cases where errors were made, families are believed to have been asked for permission, but their decisions were based on misinformation about the wishes of their relatives.

A spokeswoman for NHS Blood and Transplant said: "We are aware of issues with the records with a small proportion of the people who signed up to the NHS organ donor register.

"We are taking it very seriously and are urgently investigating the situation.

"Our priority is in ensuring that the families of those who may have been affected are contacted."

Liberal Democrat health spokesman Norman Lamb said: "This is a shocking failure of proper controls over organ donation. There needs to be a full inquiry.

"The Liberal Democrats believe in reforms to provide for assumed consent so as to increase organs available for transplant.

"But for so long as the opt-in consent system is in place it is critical that everybody has confidence in the current system."

Dr Evan Harris, Liberal Democrat science spokesman and chairman of the Parliamentary Kidney Group, said: "Today's news misses the real problem under our current opt-in system and ignores the needs of those waiting for an organ.

"The few cases that have emerged today where relatives have ended up approving donation beyond the donor's wishes are exceeded by the occasions where relatives have refused donation in the presence of a registered willingness from the donor, and dwarfed by the number of refusals by relatives of donation where the donor would have wanted to donate but was not on the register.

"In the cases that have emerged today at least the end result is the saving of lives, whereas when relatives refuse when donors would be willing, the result is that recipients die while waiting.

He continued: "While most people are willing to donate, only 25% are on the register, which means in three-quarters of cases their relatives are likely to wrongly refuse life-saving donation. So under our current opt-in system, every year the wishes of thousands of people who are willing to donate but are not on the register are disregarded because the decision is transferred to bereaved relatives.

"Only with an opt-out register for organ donation, with a presumption of life-saving consent for those who don't opt out, can the wishes of the vast majority who are willing to donate be respected."