Allegations of senior aid workers funding and supporting Hamas's military operations are only the tip of the iceberg, according to the former head of Israel's domestic intelligence agency, Avi Dichter.

Mr Dichter, now a Likud MK, said international donors were "hideously naïve" if they thought their cash was not being handed over to terrorist organisations, and many aid agencies "know very well that they are funding Hamas".

Last week, an Israeli court charged the Gaza director of global charity WorldVision with channelling aid money to Hamas's military wing.

And this week it emerged that a Gazan working for the UN's Development Programme had been arrested by Israel on the charge of supporting Hamas's terrorist operations.

Mr Dichter, who ran the Shin Bet from 2000-2005, said WorldVision was "only a small example".

He claimed "nearly 100 per cent" of officials working for the UN aid agency for Palestinian refugees, Unwra, are Hamas members.

"When you look at groups like the UN and enlightened countries that, with well-established worldviews, fall into the trap set for them by Hamas and Islamic Jihad," said Mr Dichter, "it just is amazing to see the extent and power with which it plays out year after year after year."

Fifty days after he was arrested at the Erez Crossing, Mohammad El Halabi, WorldVision's director of operations in Gaza, was indicted in an Israeli court. WorldVision is an international charity working on health and education programmes for children around the world.

El Halabi was accused of working as an undercover operative for Hamas' military wing since 2005, and of funnelling aid money to the terror group through two shell-companies that won WorldVision contracts. The full value of funds diverted to Hamas was estimated at around $50 million (£38m).

WorldVision responded that the entire value of its aid to Gaza over the past decade had not amounted to $50m and that the charity subscribed to the "humanitarian principles of impartiality and neutrality and therefore rejects any involvement in any political, military or terrorist activities". It added that the organisation had "detailed procedures and control mechanisms in place to ensure that the funds entrusted to us are spent in accordance with applicable legal requirements".

Since Friday, Israeli diplomats have been briefing their counterparts in countries where WorldVision fundraises. The Australian and German governments have already announced they would freeze their funding earmarked for the organisation's projects in Gaza.

According to El Halabi's indictment, WorldVision money funded the construction of fortifications and tunnels, the acquisition of weapons and support for families of Hamas fighters.

It also emerged this week that a Gazan working for the UN Development Programme was arrested by Israel last month for allegedly supporting Hamas.

According to the Shin Bet, Wahid Burish, 38, prioritised rebuilding efforts in areas where Hamas officials lived. It was also alleged that he helped Hamas take over tunnels built by other local terror groups.

In the wake of the scandals, this week the Israeli government announced that it was looking to deport aid agency employees found to be promoting BDS.