Pressure had been growing on the Government with MPs, council officers and waste firm representatives pushing for the change.
The Conservatives asked Parliament this week to add a clause to the Clean Neighbourhoods Bill that would make fly-tipping an arrestable offence.
But Minister of State for Local Environmental Quality Alun Michael shocked the Commons when he revealed that the bill already included such a measure.
Further inspection showed that Clause 41 makes the maximum penalty for fly-tipping five years in prison, automatically classifying the offence as arrestable.
An MRW investigation prior to this discovery revealed wide-ranging support for the law change - and no knowledge that it was already in the Clean Neighbourhoods Bill.
Labour MP Paul Flynn supported calls for arrests to be allowed for the offence, saying: "Fly-tipping is a vast and growing problem in the rural areas of my constituency."
Plaid Cymru MP Simon Thomas had added: "Yes, I'm happy to support the proposal."
Environmental Services Association chief executive Dirk Hazell said: "We support the proposal."
Reported incidents of fly-tipping grew by 40% between 2001 and 2003, with the cost to the UK now up to £150 million per year.