Ending the fees that poor people have to pay to get treatment for illnesses would seem to be both morally right and practically sound. Gordon Brown, as UK prime minister, championed the end of user fees in 2009, proudly announcing ahead of a New York summit that four countries would scrap them – Nepal, Sierra Leone, Malawi and Burundi.

But a review published this week by experts from the Institute of Tropical Medicine in Antwerp, sponsored by Unicef which originally commissioned some of the work, suggests that the switch to free healthcare just is not that simple. Most importantly, countries that take that road need help and financial support if an idealistic idea is not to end in the suffering of sick adults and children – as the drugs run out in clinics that no longer have a reliable income stream from patients. And yet, they say, "in 2011, some donors pulled out of countries after having encouraged them to remove user fees in the first place."

The review, published as a supplement in the Oxford University Press journal Health Policy and Planning, says "policies aiming to reduce financial barriers can be very effective in improving health service utilisation, provided they are well designed, funded and implemented." But they "cannot be removed with the stroke of a pen".

Unfortunately, that is exactly what has sometimes happened. Presidents, sensing a popular mood and maybe with a vote coming up, make a big announcement. And then the ministry of health has to catch up. "Electoral considerations have played a role," say health economist Bruno Meessen and colleagues in a paper looking at what happened in six countries. "For instance, in Uganda the decision was taken during the presidential election campaign under pressure of opposition candidates. In Burundi, Liberia and Uganda, the decision to remove user fees was taken by the president, sometimes in a sudden and top-down manner."

Some countries have abolished all fees, while others have removed them for pregnant woman and small children, conscious of budget restraints but in the hope of improving their maternal and child mortality outcomes.

But the pitfalls are the same. Without sound preparation and resources to compensate clinics for loss of revenue from patients, things can start to go wrong.

In all six countries [Ghana, Senegal and Burkina Faso are the other three studied], the reform was initially enforced in most facilities. In Uganda, there is evidence that this happened on a large scale and lasted for years. However there are indications that insufficient funding and, perhaps, perverse incentives, are now undermining the policy (eg households are obliged to purchase drugs from private drug outlets). In Ghana the health facilities started implementing the reform but some resumed charging when reimbursements were exhausted and debt was piling up at regional drug stores. In Senegal there is evidence that even at the start of the reform some facilities failed to provide free deliveries or only removed part of the user fee charges.

From what I have seen and been told on a number of visits to Soroti district in northern Uganda, healthcare is free only in theory. There is no charge to see the doctor or clinical officer or nurse at an out-patient clinic, (although you may have a very long wait) but drug stock-outs usually mean you have to find the money to buy not only drugs but surgical gloves, intravenous fluids and other essentials from a private shop. Worse still, some of the hospital doctors demand payment from their patients – shockingly even threatening to withhold a life-saving caesarean section from a woman, in one case, if her husband did not find the money.

Proper government funding and well thought-out systems for supplying drugs and staff to clinics may not end corruption, where it exists, but they must help. And it certainly appears from this review that donors who urge the end of user fees need to step in - and stay in - with support and money if fledgling free healthcare systems are to work as well as they possibly can.