The Norfolk Strategic Partnership started in 2004 for a period of 10 years, with provision for break points at years five and eight.
Under the renegotiated arrangement, the eight year break clause is not exercised and the contracts continue until their full term in April 2014.
There is also scope within the new arrangement for the potential transfer of additional work to May Gurney.
May Gurney Chief Executive, Philip Fellowes-Prynne, said: “We are delighted to have been awarded this contract extension with the Norfolk County Council and equally pleased with the potential transfer of further works, which is testimony to the high quality work we’re delivering for our client. This demonstrates our success at developing value-driven long-term relationships.”