The Annual Accounting for Pensions report found the gap between assets and liabilities in pension schemes at FTSE100 firms rose from £42 billion last year to £43 billion in 2013.
The main cause was continuing low interest rates, which affect the calculation of a pension scheme's future liabilities.
LCP's 20th annual report analyses the defined benefit (DB) schemes of the FTSE100 and examines the way companies deal with pension issues.
LCP said 20 years ago, virtually all FTSE 100 companies offered a final salary scheme. Today, no FTSE 100 company offers such schemes to new employees.
LCP partner and report author Bob Scott said: "With pension liabilities approaching £0.5 trillion - and with constant legislative changes, many companies will be hoping that, in 20 years' time, they have managed to completely remove any pensions risk from their balance sheets.
"This may be good news for their shareholders but is unlikely to improve the lot of those employees who are relying on good workplace pensions for their retirement."
