Two ministers vowed yesterday to stop a convicted rapist receiving his £7 million lottery winnings but no one in Whitehall could say how.
David Blunkett, the Home Secretary, said criminals in jail who scoop the jackpot or inherit wealth should not "benefit from a single penny".
Tessa Jowell, the Culture Secretary, whose department is responsible for lottery law, said the rapist, Iorworth Hoare, should not get the money and discussions were taking place to prdvent him from doing so.
"What we can do, in a very specific case like this, is to intervene and say somebody in these circumstances who is a convicted prisoner can't receive lottery winnings - that those winnings should go instead to the benefit of victims," she said on radio.
But while ministers denied they were engaged in a knee-jerk response to the outcry over Hoare's win, neither they nor their officials could say how such a law might work.
Ms Jowell admitted: "I'm not in a position to tell what the answer to that considered examination is going to be."
Their pledges, which reflected outrage in tabloid newspapers, appear to have taken Whitehall by surprise.
Powers were already being taken to pursue lottery winners to recover compensation paid to their victims.
But they conceded that nothing can be done to prdvent money being invested on the criminal's behalf or to stop interest accumulating on the sum.
They also accepted it was impossible to prdvent a prisoner on day release or a family member buying a lottery ticket.
Cash can be taken from criminals if it is the direct result of their crimes, though only after a civil court action. Yet even if a law were introduced specifically to forbid prisoners receiving lottery winnings, it is unlikely to be retrospective and would not affect Hoare.
Mr Blunkett, writing in The Sun yesterday, denied that his response to the outcry was a "knee-jerk reaction". He said a consultation paper issued earlier this year anticipated such a possibility.
It proposed that, if a prisoner won the lottery or came into an inheritance, then the Criminal Injury Compensation Authority should start proceedings to recoup from him any money already paid to his victims under the scheme.
Standard payments to rape victims range between £11,000 and £33,000.
"Few offenders are in a position to pay back authority awards," said the newspaper.
"But if the offender's circumstances were to change for the better (eg winning the lottery, gaining an inheritance, etc) then the authority would be able to initiate recovery action up until the expiry of an appropriate limitation period."
There was nothing to indicate that if a prisoner did win the lottery he should be prdvented from benefiting "from a single penny".
The Home Office said what Mr Blunkett meant was the current practice under which prisoners are not allowed to spend more than a few pounds a day on food and phone cards and the like. No new laws to strip prisoners of their wealth are envisaged.
Offenders with money could be required to pay into a general fund for victims under plans already outlined. It is also open to victims to sue through the civil courts, though there is normally a three-year "window" in which to bring an action.
Hoare has been in jail for almost all of the last 21 years and was in an open prison - which normally indicates an imminent release - when he bought the ticket. He has now been returned to a closed prison for "security and his own safety".
Boris Johnson, the shadow arts spokesman, said: "The great instinct of any politician anywhere is to get his leg over a story and say 'Well, something must be done and I'm going to do something'. The Home Secretary is no exception to that rule.
"I happen to think it would be wrong to do anything legislative to try to correct this situation."