Organisation has one of the biggest deficits among the sector

Pensioners who worked at the RSPB have raised concern after the charity stopped future accruals.

The pension fund has been closed to new members for some time and used to guarantee income to pensioners through its defined benefit scheme.

However while the charity will continue to pay into a defined contribution scheme, it will no longer guarantee a certain level of income.

“The pension liability continues to fluctuate,” the charity said. “In 2015 it stood at £86m and despite a fall in 2016 it has increased to £90m in 2017. This is largely driven by factors outside our control.

“On 31 March 2017, the defined benefit pension scheme was closed and staff were transferred to a defined contribution scheme. This should help to reduce future risk and the volatility of pension liabilities.”

The charity has guaranteed that if it cannot meet its obligations under the scheme, it will transfer land worth £57m to the pension scheme.

It comes despite the RSPB reporting record levels of income and membership.

The wildlife charity said it had topped £140m of income, including £6.7m of investment gains, up from £137.4m the previous year. Without those investment gains, income was down slightly.

Membership rose from 1.19 million people to 1.22 million.

The charity said that despite a record year, it faced challenges for the future. It said that leaving the EU would make it harder to raise money, as would the implementation of GDPR.

TFN undertook a pensions investigation last year revealing most charity leaders and staff feared for the future of their pension scheme.