Statistics published by the regulator show that between September 2016, when pilots of the 30 hour free childcare scheme began in eight areas, and March 2017, there was an increase in childcare places at seven of the eight pilot local authorities taking part.
Of the pilot providers inspected by Ofsted, there was an average increase in places of six per cent. By comparison, across England, childcare places increased by one per cent within the same time period.
York - the only local authority pilot area that funded places for all eligible children across all types of childcare provision - recorded an increase of 14 per cent.
From September, working parents in England will be entitled to 30 hours of free childcare for three-and four-year-olds, up from the current 15 hours. But there have been concerns that the government has not set aside enough money to pay for it.
Purnima Tanuku, chief executive of the National Day Nurseries Association, said a factor in York's success in boosting the number of places was providers charging parents for meals and additional services.
She is urging the government to either plough more money into the 30-hour entitlement offer or bring in mandatory additional charges to parents to make up the shortfall.
"[York] has been a success because providers have approached the pilot in a positive way and been allowed to be flexible in the way they operate," she said.
"We know through our network of members in York that nearly all nurseries there have moved to a model where they charge for meals and additional services.
"This is the only way they can offer 30 funded hours and remain sustainable due to the inadequate hourly rate they are given."
The Ofsted statistics show that, overall, the number of childminders in Egnland is continuing to fall.
Between the end of December 2016 and the end of March 2017 the number of childminders dropped by 500, with 1,400 leaving the sector and 900 joining during the period.
In total, at the end of March 2017 there were 43,500 childminders in England, a 24 per cent fall compared with August 2012.
The Pre-school Learning Alliance has warned that the sharp decline in childminder numbers will leave the government struggling to implement the free childcare expansion in September.
"It is incredibly concerning to see such a continued decline in the number of childminders," Neil Leitch, chief executive of the organisation, said.
"Childminders are a vital source of quality, flexible early years care and education and yet, every time Ofsted releases new statistics, we see yet another fall in numbers. This is simply not sustainable.
"With the implementation of the 30 hour offer imminent, childminders will play a vital role in delivering the flexible childcare that government has promised to parents. The question is, then: why isn't more being done to address this worrying trend?"
Liz Bayram, chief executive of the Professional Association for Childcare and Early Years said the data reinforces her organisation's previous call for urgent action at national and local government level.
"Without renewed efforts to recruit new childminders and to support current childminders to remain in the profession, children and families will not benefit from thus quality, flexible form of childcare.
"The 30 hours offer could support more childminders to run sustainable businesses but only if local funding levels are high enough and there is an ongoing local focus on supporting individuals to enter and stay in childminding.
"We know some local authorities do this really well. But they are the minority and we need the DfE to do more to champion childminding with local authorities and, through its workforce plans, show how childminding is valued and rewarded as a profession. Without this action, sadly this trend is only set to continue."