By John Ware
BBC Panorama reporter
Interpal has denied having any links to Hamas
The Charity Commission has launched a formal investigation into the London-based Palestinian charity Interpal.
The commission says there are "concerns about the potential for indirect and inappropriate links" between Interpal "and organisations or individuals who appear to support the militant or terrorist activities of Hamas".
The announcement follows an investigation last summer by a Panorama programme Faith, Hate & Charity, which said funds from Interpal had helped build support for Hamas.
Interpal has twice before been investigated and cleared by the commission which regulates charities.
Hamas is outlawed by the European Union as a terrorist organisation.
In the programme, young girls at a children's charity in Hebron - which Interpal has helped fund - were seen glorifying suicide bombing, encouraged by adults.
Interpal say they do not condone such songs.
Following the programme, the commission said it would assess whether a third formal investigation was merited after analysing evidence supplied by the BBC and seeking a response from Interpal's trustees.
The commission has now decided that the evidence does merit a more detailed investigation than the last one, which they admitted was "not in depth."
The inquiry will be held under Section 8 of the 1993 Charities Act.
A commission spokesman told the BBC that an S8 inquiry was the most serious form of inquiry, giving them wide powers of investigation including the freezing of funds - though at this stage there was no intention of doing this.
The programme showed how Interpal's Managing Trustee Dr Essam Yusuf doubled as the key trustee for a coalition of Islamic charities chaired by Dr Yusuf Qaradawi, who has championed suicide bombings in the Israel-Palestine conflict.
The commission says that its new investigation will include the duties and responsibilities of Interpal's trustees.
Interpal has categorically denied having links to Hamas.
It insists it allocates humanitarian aid mostly to Islamic charities in the West Bank and Gaza, solely on the basis of need.