When Ruth Wollacott met Tony Blair shortly before the general election, she was surprised to find that he was not the character she had imagined. He was neither smarmy nor false, and seemed genuinely concerned that her son had caught MRSA and nearly died at the age of 19.

When he promised to help her she believed him. Now, after writing letters to Downing Street, she believes that, like his ministers, he had no intention of taking the matter seriously and simply used the issue to help his election chances.

Her son, James, is now 21 and can only walk with crutches. He caught MRSA from a London hospital two years ago after a simple operation for a dislocated knee. His future as a maintenance worker looks doubtful, and he has been on benefits for two years.

James will need further operations to reconstruct his knee, which has damaged tissue following the infection. He is in pain every day.

The effect on his family has been dire. His mother has had to give up her full-time job to help look after James, and they have remortgaged their home in Hornchurch, in east London.

'We have been abandoned,' said Wollacott. 'We are the hidden victims. People assume this superbug affects only the elderly but, in my son's case, it attached itself to the metal pins which were put into his knee. He very nearly died.'

In her hand are cuttings from newspapers on the day last April when she met the Prime Minister. She gave him a list of 'hidden victims' - such people as her son who have never been classified as MRSA sufferers by hospital trusts, but have been diagnosed with it.

She told him: 'My son contracted MRSA in hospital two years ago and he's now crippled. Why are you pretending MRSA isn't happening?'

Blair responded by saying: 'We're not pretending it's not happening. And I'm really sorry about what has happened to your son. I've never said MRSA is not a problem, I've just said it shouldn't be treated as if it's the only problem.'

Since then, Ruth and Martin Wollacott have tried to contact Downing Street to discover more about the present flawed system for recording infection rates, and to see whether Blair ever looked into the matter.

'We have sent two letters asking him to look at the list of people who don't end up on the official list of victims, but each time we are told to contact the Department of Health because he is too busy to deal with it,' said Mrs Wollacott. 'He wasn't too busy to take a personal interest in it before the election, but he is now.'

Since the election, Health Secretary Patricia Hewitt has announced that trusts must do far more to get to grips with the superbug problems. The government has claimed there are signs of progress in the battle against MRSA as the number of cases in October-March 2005 was 6.4 per cent lower than in October-March 2004, when 3,940 cases were recorded.

Health Minister Jane Kennedy said it was the first time there has been a fall in MRSA blood infections since a mandatory reporting system was introduced four years ago.

But a report by the Commons Public Accounts committee was highly critical last month of the lack of clear information about cases.

It pointed out that at least 300,000 people a year pick up an infection, and that there is still a shortage of isolation rooms to stop infection spreading.

The report concludes: 'The Department [of Health] still does not have a grip on the extent of infection. What evidence there is suggests things have got worse.'