The organisation raised money to fund education programmes in schools and communities, and had high-profile backers including former Principal Family Court Judge Peter Boshier, former Auckland Grammar School headmaster John Graham and Auckland Crown Solicitor Simon Moore, QC.
Yesterday Mr Moore said the trust had been very effective and its problems were related to fundraising only.
"As with so many voluntary organisations, particularly in these difficult times, it suffered from funding. And without funding it couldn't achieve its objects."
The decline in funds was not related to Sir Paul's death this year, Mr Moore said, although the broadcaster had been a tireless ambassador.
"It was wonderful to have someone with that kind of profile ... he was very energetic in terms of his support and promotion of the trust."
A recent progress report on the Government's Methamphetamine Action Plan showed the number of P users had more than halved since 2009.
Mr Shipley would not reveal which sponsor had pulled out, nor the total amount of money needed to keep former operations going.
It was a "big project", which was not necessarily over, he said.
"The intellectual property is still there, and if at some stage we can pull together some funding for it, you'll see us back in the marketplace."