The nation's stock of council-owned farms are a vital asset to the whole agricultural industry, which must not be allowed to disappear, warned tenant farmers' leader George Dunn.

They allowed young people wanting to enter farming to get going, beginning as tenants, he stressed.

He was speaking in support of Sir Don Curry's call for action to preserve a "farming ladder" in British agriculture.

Sir Don presented a paper on attracting young blood into agriculture at the Royal Agricultural Society of England's The Next Generation conference at Stoneleigh Park last week.

Mr Dunn, chief executive of the Tenant Farmers' Association, warned about the erosion of council-tenanted farms, as local authorities sold off holdings to balance their budgets. It was a warning particularly appropriate to the South West region, where the TFA has more than 2,000 members.

Mr Dunn said: "For the vast majority of individuals who would seek to enter the industry from outside agriculture, farm tenancies remain the only viable route available.

"It is only within the security of an agricultural tenancy that farm businesses without access to owned land can become established, remain sustainable and improve."

He stressed that for many years, county council smallholding estates had been a significantly important part of the landlord tenant system. But it has been alarming to view the extent to which the size of the sector had diminished over the past 25 years.

He said: "Over that period of time we have lost around half the number of holdings, and a third of the area. We believe that more needs to be done to protect county farms for the future of our industry, and to that extent the TFA has been pleased to see that a number of local authorities, including Devon, Norfolk and Hampshire have been taking a longer-term view of their county farms estates and making the decision to retain them and manage them more effectively."

But he warned that others – including Somerset – continued to take a "blasé approach" to the management of their estates, which focused only on disposal.

Last month there was consternation on three tenanted farms in Somerset, when tenancies up for standard renewal were not renewed by the local authority, which said the situation was being reviewed.

Earlier this year Devon County Council decided to lengthen the period of tenancies, so tenants were not turned out of holdings just when they were getting established, following complaints an a public protest at County Hall, Exeter.