National Trust has announced the closure of its defined benefit scheme after continued growth in the fund’s deficit.

The £447m (€540m) National Trust Retirement and Death Benefits scheme was closed to new entrants in 2003, with the charity at the time launching a defined contribution (DC) arrangement for new employees.

In a statement, the charity said it agreed with the trustee to increase its deficit reduction payments from £3m to £8.5m from 2016 onward, with the payments increasing by 1% above the consumer prices index each year until 2029.

It estimated that the deficit, which stood at £69m following its last triennial valuation in 2011 had since increased to around £116m, resulting in the 60-day consultation to close to new accrual.

“We have made these proposals now because we feel we can no longer sustain the level of cost and risk associated with providing a defined benefit pension scheme without it impacting on our ability to fulfil our core purpose of looking after thousands of special places on behalf of the nation forever, for everyone,” the charity, which maintains buildings of historical significance across the UK, said in a statement.

According to its most recent annual report, from 2013-14, the charity expected members of the fund to live to 89, with female life expectancy increasing two years by 2033.

At the end of March, the fund had £106m in bonds, £47m in derivatives and swaps and £290m in equities – which returned 7.7%.

In other news, the UK government has welcomed a report on how to increase participation of workers over 50 in the workforce.

The report by Ros Altman was commissioned by the Department for Work & Pensions (DWP) and examined the importance of an active, older workforce at a time when employees could no longer rely on guaranteed income.

“As pension provision moves to less generous defined contribution pensions, millions of older people will not be able to rely on a decent level of later life income, especially as annuity rates have fallen and investment returns have not met expected forecasts,” it said.

It argued increasing the number of workers over 50 would have a number of benefits – not only improving economic growth, but lowering the amount of money spent on benefits and improving overall intergenerational cohesion.

Altman also recommended the government consider a permanent role across all departments to extend working lives.

Pensions minister Steve Webb, one of the two ministers for whom the report was prepared, recently called for the creation of a Department for Pensions and Ageing Society.

The Liberal Democrat suggested the department be responsible for occupational and state pension policy – currently with the DWP – pension tax affairs (the responsibility of the Treasury) and old age care (overseen by the Department of Health).