The county council is reducing the amount of funding it pays to childminders for threeand four-year-old places for 2015/16 by 34.8 per cent, from £5.06 to £3.30 per hour.
Childminders with children from disadvantaged areas will receive a slightly higher rate.
Norfolk County Council said the move is designed to bring childminders in line with other early years providers.
According to the Government's benchmarking tool, on average, private, voluntary and independent nurseries in Norfolk received £3.75 per hour to deliver the places this financial year.
The council is also introducing a new funding formula, which it says will create a 'much fairer and simpler system.' A Norfolk County Council spokesperson said, 'We are not reducing the total amount of early years funding, but we are changing the allocation of the funding to better align it to the county council's Early Help strategy and ultimately meet the needs of more families in Norfolk.
'The new formula is affordable. Many more providers will benefit from an hourly rate increase, in particular those that have children who live in disadvantaged areas, and those that provide good-quality, flexible provision.
'The change in rates for childminders is to support fairer early years funding that supports children who are disadvantaged or at risk of underachieving.'
However, childminders in Norfolk have raised concerns that the drop in funding will impact on the resources and quality of experience they can offer, and warn it will ultimately mean that childminders will cease offering the free places.
As such, they have launched a petition on the Change.org website calling on the council to protect the funding.
Tanya Bunting, who runs Norfolk childminding service Tanya's Tots 2 Teens and cares for two-, threeand four-year-olds, said, 'I've worked out that the drop in funding will mean a loss of about £500 per child over the summer. I often take the children on trips, which I pay for out of my budget, but with the funding reduction I'll have to ask parents for more money to cover this.'