The plan to transfer confidential medical records to internet servers run by companies such as Google and Microsoft is anything but straightforward.

The chance for patients to have 24-hour access to their doctor’s notes on password-protected websites will appeal to the middle classes and the “worried well” who already diagnose their ailments with the help of the internet. But there is a welter of ethical and practical difficulties that could yet scupper the idea and must be considered by Francis Maude and his Tory policy implementation unit before the plan can be approved.

The most pressing issue is that almost nine million households in Britain do not have access to the internet. Health experts fear that such a move could penalise the most vulnerable in society. What disadvantage would this mean for the elderly, infirm and technologically inept? And who will store the medical records of those who do not take part?

More chillingly for some is the question of how commercial companies such as Microsoft and Google intend to make money from such ventures if, as seems likely, there are no government contracts on offer and it is left up to individual patients to chose to sign up to a number of free services. “Google is not magnanimous. It will no doubt sell that information at some point,” said a leading health analyst.

Suggestions that Google could display drug or other advertisements based on an individual’s health record, or sell anonymised data for drug trials, have been strenuously denied by the company in the US. Privacy campaigners are nevertheless likely to be concerned.

It has even caused friction within the Tories. The plan is part of a bigger “open source” IT project led by George Osborne’s team, but some staff working for Andrew Lansley, the Shadow Health Secretary, believe that there may still be a need for a central health database in the end. How else, they ask, would a hospital be able to access the medical record of a patient who comes into A&E unconscious and unable to grant them online permission?

The chance for massive cost savings, however, are likely to outweigh these objections: it must seem a hugely attractive alternative to the longoverdue £12.4 billion NHS computer project that Tony Blair promised would provide electronic health records for up to 50 million patients. “You don’t need a massive central computer to do this. People can store their health records securely online; they can show them to whichever doctor they want,” David Cameron has said.

“But best of all, a web-based version of the Government’s bureaucratic scheme like Google Health or Microsoft Health Vault costs virtually nothing to run.”

Unlike in the US, the Tories say that NHS trusts will not be handing out contracts to Google or Microsoft, and that patients will be allowed to chose whether to take part.

“We can 100 per cent guarantee that we will not have a system where there is an exclusive deal on health records with one company,” said a Tory source. “We fully expect there to be multiple providers that will almost certainly be free to users.”

The health plan is a small but highly controversial part of a Conservative agenda to use data currently held by the Government to give consumers more choice, decentralise and, perhaps most importantly, cut costs.

The party points out that there are more than 100,000 public bodies in Britain that produce a huge range of information. It believes that there are significant benefits in publishing the data in standardised and open format, so that it can be plugged into online maps, websites and other applications.

The Tories have been struck by the innovative website theyworkforyou.com, run by the charity mysociety.org, which analyses and republishes data about MPs in a user-friendly manner in a process known as mashing. They want to do the same with the rest of the public sector.

“Some of our key reform policies, for example school reform, depend on this type of information being released to the public, and so enabling effective choice and accountability to be exercised,” said a recent Tory plan.

At the moment, only a fraction of this is available, but in an aggregated and anonymised format. Norwich Union, the Tories say, spent £5 million to develop a UK flood map, which was cheaper than trying to use existing government data.

Mr Lansley has already announced that in health, commercial websites will be able to bid for the data collected by the Department for Health, allowing them to publish ward-by-ward comparisons on everything from cleanliness to readmission rates.

Dr Foster Intelligence has been awarded a £12 million contract to provide NHS hospital league tables. The Tories say that if the underlying data were published, these league tables would be built by charities and companies without any cost to the taxpayer.

At the moment a small amount of data is provided for patients on the government website NHS Choices, but doctors have expressed concern at the way it is used to rank hospitals.

The Conservatives’ agenda does not come without risk. It will inevitably be associated with Steve Hilton, one of Mr Cameron’s principal advisers, who is married to Rachel Whetstone, the head of communications for Google. According to The Register, the technology newspaper, Google and Microsoft have lobbied hard to get their hands on medical records in the US and elsewhere, and the broader “open source” project is likely to work in their favour.

Explore Health

• Expert Advice

• Health Features

• Mental Health

• Alternative Medicine

• Child Health

• Health Club