England is “a decade away” from decent mental health services for all children despite years of government announcements, the children’s commissioner has warned.

In her third annual children’s mental health report, Anne Longfield has acknowledged there has been tangible progress, but has said there remaine “a chasm” between the services currently available and what children actually need.

The report, published on Thursday, highlights the continuing postcode lottery many families face, with some areas spending 10 times more than others on children’s mental health care.

As a result, the chances of getting treatment vary hugely across the country. In four well-served areas, 90% of the children who are referred actually enter treatment; elsewhere fewer than half of referrals result in a child entering treatment.

According to the report, 93% of children in the care of Southwark clinical commissioning group in south London who were referred to mental health services entered treatment. In contrast 64% of children referred to mental health services in Knowsley, Merseyside, did not.

Waiting times have gone down slightly. On average, children wait just under eight weeks to enter treatment (53 days, down from 57 days a year ago). The report also flags up the spending gap between services for children and adults, with £225 investment on average for every adult compared to £92 for every child.

“There has been welcome progress on children’s mental health services over the last couple of years, and more progress is promised over the next few years,” said Longfield. The report says an extra £60m has been invested in specialist children’s mental health services and an additional 53,000 children have entered treatment.

“Nevertheless, there is still a chasm between what children need and what is being provided. More children are seeking help for their mental health and the government need to make sure that help is available. We are still a decade away from a decent mental health service for all children.”

Longfield questioned whether the NHS and government were facing up to the scale of the problems in children’s mental health. “The government doesn’t have a plan for a comprehensive service in every area and there is still no commitment to a counsellor in every school, which would make a huge difference.”

Many teachers are concerned they often find themselves in the frontline caring for children with mental health issues. Dr Mary Bousted, joint general secretary of the National Education Union, said government plans on children’s mental health were not ambitious enough.

“There is a clear need to end the postcode lottery of provision and ensure there is a comprehensive and joined up approach to mental health support in every area. Schools have a role to play and must be part of the strategy to address the current lack of both specialist and low-level mental health services for children and young people.”

The mental health minister, Nadine Dorries, said: “As the children’s commissioner highlights, major improvements to children and young people’s mental health care are already well under way, driving forward progress so every child can access the high-quality care they need and deserve.

“Spending on children’s mental health is growing faster than spending overall in the NHS, backed by an extra £2.3bn investment in mental health per year. We’re rolling out dedicated mental health support teams in schools and trialling four-week waiting times in the NHS, so they have quicker access to an increased range of support and treatment when they need it.”