More parents in Lancashire are using the government-funded 30 hours a week of free childcare.
The scheme was introduced in the autumn term of 2017, to provide additional free care for three and four-year-olds.
Latest figures show that in the most recent autumn term 6,903 children had taken up places, an increase of 21 per cent on the previous year.
The Pre-school Learning Alliance, which represents childcare providers, says that underfunding means that for many parents the childcare is not completely free and they end up "picking up the Government's tab".
A Department for Education survey found that 19 per cent of families found it difficult or very difficult to pay for childcare. One fifth of parents did not realise that additional charges for meals, nappies and some activities could be made by childcare providers under the 30 hours scheme.
Pre-school Learning Alliance chief executive Neil Leitch said: "We know from a study the Government itself commissioned, for example, that over half of parents accessing 30 hours said they had to pay charges for additional items or activities. And the reason for these charges is clear: providers are worried they won’t survive the next 12 months unless funding changes so feel they have no choice but to ask parents to pick up the Government’s tab."
The 30-hours entitlement doubled the hours of free childcare for some parents. All parents are entitled to 570 hours a year but this was increased to 1,140 for some - the equivalent of 30 hours over 38 weeks of the standard school year. Parents can spread fewer hours over more weeks.
The scheme is open to families where both parents are working, or the sole parent is in work in a single parent household. Each parent must earn the equivalent of 16 hours per week at national minimum wage but less than £100,000.
Across England, 240,000 places were taken up over the autumn term.
Government funding for the scheme is given to local authorities who make payments to service providers.
Funding varies across the country, based on a formula of a basic rate plus additions, depending on the needs of children in the area.
In the current financial year Lancashire council receives an hourly rate of £4.30 per child.
Children and Families Minister Nadhim Zahawi said: "It is fantastic that in the first year of delivery, over 340,000 children benefited from a 30 hours place, meaning parents are spending less on childcare and are able to increase their work hours or work more flexibly.
“We will be spending around £6 billion a year on childcare support by 2019-20 – a record amount. This is more than any other government and this support will make childcare more affordable and more accessible.”