A new trail along the east coast of England should be created, a Tory thinktank has said, because farmland is preventing those who live there from having access to nature.

A report from Onward has found that in most rural areas, people enjoy extensive rights-of-way networks. But across the east of England, there are many areas where people have barely anywhere they are allowed to walk in the countryside. This, the report says, is because of large areas of high-grade farmland in that area, but also because Lincolnshire has the largest backlog for recognition of historical but unrecorded rights of way, with more than 450 outstanding applications.

According to green space metrics created by the Department for Environment, Food and Rural Affairs and the nature charity Wildlife and Countryside Link, half of local authorities in the worst 10% for access to nature are in eastern England. Almost nine-tenths of local authorities in the east have below-average access to green space.

The government is now doing a review into the 41,000 miles of historical but unrecorded public rights of way, where people once had a right to walk but now do not as they are not officially recorded by local authorities.

A new North Sea national trail should be created from the Humber through the Lincolnshire Wolds, then across north Norfolk to Norwich, the report says.

The report found that a third of people in England currently do not have access to nature nearby, and people from ethnic minorities, younger people, and those living in more deprived areas are much less likely to have green spaces within easy walking distance.

The previous Conservative government outlined plans to make sure everyone lived no more than a 15-minute walk away from a green space, but shelved these. The Labour government has promised to increase access to nature by working with landowners to create new “river walks” alongside waterways and a new national forest.

Creating access to green space is cost-effective because it can be cheap – and sometimes free. The report says it saves the NHS more than £110m a year from fewer GP visits alone, and that £2.1bn of annual health costs could be saved if all of England had good access to nature.

The report also suggests incentivising farmers to give up small portions of their land for rights of way so people who live in the middle of high-quality farmland can go for a walk in the countryside. It suggests using the post-Brexit environment land management schemes, which pay farmers for providing public goods, to do this.

Ed Winfield, an author of the report, said: “England’s green spaces are a great source of national and local pride. But for many, nature is too far away or too difficult to access. Creating a new North Sea national trail across eastern England will address the country’s most significant access-to-nature gap, while other initiatives such as recording historic rights of way and integrating nature into planning decisions can overcome local nature ‘notspots’.”