Stratford-upon-Avon ranks in the top 20% of rich districts
The financial gap between north Warwickshire and the more prosperous south is widening, according to a county council report.
The borough of Nuneaton and Bedworth was found to be the worst performer in 13 out of 16 areas used to indicate poverty, such as income and employment.
It said residents were poorer than in 2004, despite moves to close the gap with Warwick and Stratford-upon-Avon.
The county council said investment in the borough would continue.
Nuneaton and Bedworth was not only the "most deprived" borough in the county, it had also "moved into the top third" position in England, the report said.
In contrast, Stratford ranked within the top 20% of least-deprived districts in the country.
"The clear message was a confirmation that there is a significant gap within Warwickshire," the report said.
"This, in most cases, can be specified as a distinction between Nuneaton and Bedworth and Stratford-on-Avon/Warwick districts."
It said that what was of "greater concern" was that of the 13 indicators that could be tracked over a number of years, only two demonstrated a reduction and "in some cases the gap continues to grow".
The 16 indicators of poverty include infant mortality, teenage pregnancy, and GCSE attainment.
The report also said since the launch of the national lottery in 1995, people in Nuneaton and Bedworth had received only £103 per person, compared to £609 per head in Stratford.
Colin Bell, the report's author who has worked on regeneration projects, said: "The aim is to improve the life for residents in the borough, in terms of job opportunities, training and quality of life."
He said the reason behind the borough's lack of wealth was mainly "historical" and related to mine closures and loss of manufacturing.
Mr Bell said there had been progress, but the borough needed a long-term strategy, which included encouraging new firms into the area, improving training and education and helping people set-up businesses.
Warwickshire County Council said it had been working on a number of initiatives designed to "close the gap" and many developments in the borough were "bearing fruit".
Councillor Chris Saint said: "Whilst we are mindful of the gap, we should not let that stop us from celebrating some of the many good things that have been happening in Nuneaton and Bedworth in recent years."
He said average earnings in Nuneaton had risen to nearly £24,000 in 2007, less than 5% below the county average, and further investment should see this rise continue.
Mr Saint added GCSE results in the borough had been improving "year on year", while attractions such as the George Eliot festival have been increasing visitor numbers.