Sussex Enterprise created 800 jobs and helped businesses to an extra £230 million in pre-tax profits between 1995 and 1998, according to its latest report.
The business support agency surveyed 540 local businesses to reach the figures. It compared firms which had worked with Sussex Enterprise with those who had not.
Sussex Enterprise chairman John Peel said: "I hope this will encourage more local businesses to make use of the wide range of tailored services we have for them."
Mark Froud, director of economic research at the agency, said: "Over the period, businesses using our services increased productivity by nine per cent and doubled their profitability.
"Eighty per cent of the improved profitability was re-invested in the businesses to promote future growth."
He admitted he could not be sure the improved performance these firms was wholly due to the work of Sussex Enterprise but said he believed a "significant proportion" was due to the agency's efforts.
It found firms using its services increased turnover by 37 per cent (compared to a three per cent average for all Sussex businesses) and saw pre-tax profits leap by 184 per cent (compared to a 60 per cent average).
Sussex Enterprise chairman John Peel has joined the board of the British Chambers of Commerce.
Mr Peel, who is managing director of Crawley-based Varian Medical Systems, said the move would benefit Sussex firms.
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