Negative equities and falling bond yields have helped drive the UK's final salary pension schemes back into deficit over the past 12 months, a new report from the Pension Protection Fund (PPF) has revealed.

Research carried out by the body found that the 7,800 final-salary schemes analysed had a total deficit of £24.1 billion at the end of July, a dramatic drop from the £8.3 billion surplus recorded in June, while the same funds were also £83.3 billion in the black at the same time in 2007.

"Over the past year, the negative impact of equities on scheme assets, combined with falling bond yields, have led to an overall worsening of the funding position," the PPF report read.

"With lower bond yields resulting in an 8.6 percent increase in aggregate liabilities, while weaker equities have reduced assets by 7.4 percent."

The report comes just days after actuarial firm Lane Clark and Peacock showed that the pensions funds of FTSE100 companies recorded a collective deficit of £41 billion in July, representing the biggest swing from a position of surplus seen since 2002.

Furthermore, according to the BBC, KPMG has warned of a potential "pensions crunch" looming as trustees call for more investment at a time when businesses are struggling financially.