Rejected asylum seekers and illegal immigrants should get HIV treatment free on the NHS like everybody else, to avoid the risk of a further spread of Aids, a Commons select committee said yesterday.

In a strongly worded report, MPs on the health select committee said the government's withdrawal of free treatment from these groups as a measure against "health tourism" was ill-advised.

While it was vital that the UK did not become a magnet for HIV positive people seeking free treatment, "we have seen no evidence that this is happening", David Hinchliffe, the committee's chairman, said.

Under new government rules, treatment with the antiretroviral drugs that can prevent infection with the virus progressing to Aids is no longer available to people found to be illegal entrants or those who have had an asylum application turned down. The treatment can cost between £10,000 and £14,000 a year.

Although there has been controversy about people allegedly arriving to get free treatment, the select committee says the government has no idea of their number, or how much they cost the NHS.

On the other hand, the threat to public health is clear. "The Health Protection Agency, the government's own public health advisory body, told us that if these individuals are not treated, and they remain sexually active in this country, then transmission is bound to go up," Mr Hinchliffe said.

Migrants with HIV generally do not seek treatment until they have been here for some time and their disease is well advanced, the committee says, which is not the behaviour of a health tourist.

The MPs point to an anomaly, in that people with tuberculosis are exempted and can be treated for their TB even if they are here illegally. Yet increasingly, people with HIV have TB as well.

"If their underlying HIV is not treated because of cost, they may then default from care and as a consequence transmit TB to as many as 15 people a year.

"It is a nonsense that the government is prepared to fund a person's TB treatment on public health grounds but not treatment of his HIV infection."

The report says the committee is "deeply concerned that neither the department nor the public health minister appear to have considered or understood the public health implications of refusing HIV treatment to people who, although not legally resident, continue to live in this country".

It will deter them from being tested, and if they do not know they have HIV they are more likely to infect others. Moreover, taking the drugs makes it up to 60% less likely that people with HIV will pass the virus on.

There are about 53,000 cases of HIV in the UK, and the number diagnosed is rising by about 20% a year. In 2003, 6,606 new infections were diagnosed, the Health Protection Agency says.

The report paints a generally dire portrait of sexual health services in the UK.

Two years ago the committee said there was a crisis: overwhelmed clinics sometimes operated in portable buildings and people with sexually transmitted infections had to wait weeks for an appointment.

This follow-up report says cases have continued to rise, waiting times are still bad and the services "are more overstretched than ever".

While they welcome the government's recent announcement of a campaign to educate about sexually transmitted diseases, they say the current services will not be able to cope with the inevitable increase in demand.

They recommend the government to postpone it.

The committee welcomes the new money the government has given to the sexual health services, but says it is not enough. It calls for an audit to establish how much is getting through and how much is diverted by primary care trusts to other parts of the health service.