It has been billed as the event when the world will come to London. It has been over 60 years since this country last hosted the Olympics - and this year's event will be very different from the last time the Olympic Torch was carried into the capital in 1948. The Olympics is big business: it is likely that the games will provide a welcome boost to the British economy, with an additional 330,000 international visitors to London this summer.

But with such a large number of foreign visitors in the capital this year, this has the potential to present significant challenges to our public services - in particular the NHS. The majority of these visitors will not be eligible for free NHS care - so will have to pay for any medical costs incurred during their visit. However, experience tells us that recouping this money is no small thing.

Last year, using Freedom of Information requests, I carried out an investigation, which asked every NHS Foundation Trust for the amount of debt owed by foreign nationals - both written off and unpaid. By October 2011, I had gathered responses from over 118 trusts, showing that that more than £40 million had been written off or was still outstanding - and past performance suggested that even the payments still due were unlikely to be recovered in their entirety. Guys and St Thomas' managed to rack up the most impressive deficit, with over £6 million being written off since 2004.

Even more worryingly, in 2008, a poll of NHS managers responsible for overseas visitors revealed that a third did not even routinely ask patients about their eligibility for free care. This suggests that there is a further category of foreign nationals who are receiving free care that they are not entitled to, and due to substandard administration, the details of this are not even being recorded.

Whilst the current government's assurances of action on this issue are welcome, we should look at more ambitious ways to tackle the problem of overseas visitors leaving the country without paying their bills.

It is important to have tough structures in place that prevent people from exploiting the system. In some areas action has already been taken to limit this problem. West Middlesex University Hospital introduced a 'stabilise and discharge' policy for foreign nationals, where doctors ensure that the patient is not in immediate danger. They are then told what treatment is required, the cost of it, and if they are unwilling to pay, they are asked to leave. This pragmatic policy is the reason that West Middlesex University Hospital only saw a tiny amount of debt written off, despite the fact that it is the closest hospital to Heathrow Airport.

At Southend Hospital, doctors and nurses now ask all patients whether they have lived in the UK for at least a year, and will also cross check this against previous medical records and ask for proof of address. Tests like these ought to be standard practise across the country.

It cannot be right that in an age of financial pressures and tight budgets, taxpayers are being asked to pay up front for the care of foreign patients, who then fail to pay back what they owe. It is simply a question of fairness. Tackling this problem cuts across all levels of the NHS - both hospitals and GPs have a role to play in ensuring the proper registration of overseas patients. And politicians have a responsibility to show leadership on this issue - to decide where rights and responsibilities meet, and to ensure that our health service reflects this. This is particularly important at a time when we will be welcoming a large number of additional visitors to our country. We must ensure that Olympic tourism does not turn into health tourism.