Hundreds of Sussex families will lose vital care and support if a charity for autistic children does not raise tens of thousands of pounds in the next six weeks.

Sussex Autistic Society has provided specialist services such as respite care and day centre places for up to 500 families in Sussex for the last 25 years but may have to shut down because of massive funding shortages.

Last Thursday, the charity's executive committee agreed to suspend sessions at two family centres in Eastbourne and Rustington, near Worthing, as well as two parent groups in Brighton and Crawley.

Crucial respite care for dozens of families with autistic children could be stopped within the next six weeks if the charity cannot find £20,000 to ensure its survival. The charity's shortfall is partly the result of setting up fee-generating respite care services.

Its outreach respite care scheme is expected in time to bring in income from fees but this has not grown as fast as hoped. More staff were taken on since the service was launched in October last year but the charity has not yet made enough to pay for them.

It has also launched a play scheme which has eaten away at its funds. Staff said the charity was, therefore, a victim of its own success.

The charity has also struggled to raise funds during the last year and the lack of donations has added to the shortfall. Fund-raisers suspect they have lost funds to appeals for victims of the Asian tsunami and the latest earthquake in Pakistan. Many British charities have lost millions of pounds as a result of tsunami fund-raising.

Ranti Fallowfield's seven-year-old son Jacques attends alternate weekly sessions at the Southdown Family Centre in Station Road, Rustington. The family also benefits from two afternoons of respite care a week.

Mrs Fallowfield said: "The news has been devastating. The society is our life-line."

She said Jacques, who was diagnosed with autism when he was two and cannot speak because of the condition, loved the play sessions put on at the centre.

She said: "I'm worried his behaviour will deteriorate and he will become more aggressive without it." Mrs Fallowfield, who lives with her husband Rick, Jacques and their daughters Rebecca, 15, and Kirsty, nine, in Littlehampton Road, Wortaid, said loss of respite care would have a serious effect on the whole family.

The society needs £5,000 a month to run and needs an immediate cash injection of £20,000 to continue.

Lisa Perks, from the charity, said the crisis was ironic as this year has been its most successful with the introduction of outreach respite care and outstanding inspection reports from Ofsted and the Commission for Social Care and Respite Care.

She said the charity's 23 staff, mostly based in Hassocks, would lose their jobs before Christmas if the money couldn't be found.