Terence Hart stole pounds 17,000 and spent it on cannabis, horse racing, a new car, carpets for his home and a honeymoon in Tunisia.
Hart, 36, worked for the Luton branch of Mencap for just 14 months but in that time stole the equivalent of 18 months' fund- raising.
Hart, of Elgar Path, Luton, was jailed for three years after pleading guilty to three charges of theft, three of forgery, and asking for 13 similar offences to be taken into consideration. The offences, which took place between 28 February 1991 and 7 January 1992, were sample counts.
Stuart Trimmer, for the prosecution, said Mencap took him on without references, despite Hart's previous convictions for theft, burglary and fraud.
Mr Trimmer said the thefts came to light when a Mencap official went to the bank expecting to find around pounds 10,000 in the charity's account but instead discovered there was less than pounds 1,000.
Simon Reid, for the defence, said his client, a reformed alcoholic, expressed remorse.
The recorder, Colin Hart- Leverton, said: 'This was a particularly mean crime against some of the weakest people you could imagine.'
After the case, Irene Harris, of Luton Mencap, said: 'We took in this man and gave him a chance. He threw it all back in our faces. It has completely ruined my faith in human nature.'
Mrs Harris said the charity was selling its Avondale Road headquarters which had been put on the market at pounds 220,000.Reuse content