One of the community's leading Israel charities, JNF UK, has suffered a massive drop in contributions, with voluntary income plummeting by more than half from 2010 to 2011.
According to its newly-published accounts, income from donations, legacies and investments fell from around £5.1 million in 2010 to just over £2.4 million last year.
The collapse in its income contrasts with the leading British Israel charity, the UJIA, which has experienced a far more modest 13 per cent fall in comparative income over the same period, from £14.3 million to £12.4 million.
It is four years since JNF UK's chairman Samuel Hayek took over from Gail Seal as part of a deal to end a costly legal conflict with its Israeli associate Keren Kayemeth LeIsrael (KKL).
The dramatic fall in its revenues has been blamed on a perceived politicisation of the charity by Mr Hayek.
At the end of 2007, JNF UK posted an income of more than £8 million, but that yield has slid in successive years. In 2011, donations fell from nearly £2.6 million in 2010 to just over £1.5 million last year, and legacies from nearly £2.5 million to £832,000.
A senior communal figure said: "This collapse in philanthropic support is the clearest possible signal that the community no longer the sees the JNF, under its current leadership, as a credible receptacle for its charitable support for Israel. On the basis of these accounts it is questionable whether the JNF can any longer accurately be described as a major communal organisation. Its long-term sustainability looks uncertain."
But Daniel Frohwein, JNF UK's head of marketing, said that its viability remained "strong. We have a level of reserves which enables us to support our commitment in leaner years." Legacy income would "always be variable and understandably outside our control".
The JNF's response to lower income levels was to "restructure departments and professionally manage our expenses in line with our income."
JNF UK cut its support costs from £1.7 million in 2010 to just over £1.2 million last year - although that figure does not include another £400,000 or so for fundraising and publicity last year.
The charity sent £2.3 million to Israel last year.
A report of JNF's activities accompanying the accounts states that it held a successful annual dinner for 250 guests in 2011 but does not say what, if any, money was raised.
The £2.4 million income excludes £7.5 million raised through a JNF subsidiary, KKL charity vouchers, which is a conduit of funds for other charities.