Total deficits of defined benefit (DB) schemes exceeded £300bn for the first time in May reaching record levels, according to JLT Employee Benefits.
Its latest monthly statistics for all private sector DB schemes showed the gap between assets and liabilities widened from £294bn in April to £310bn in May.
The total DB funding level slightly fell from 81% to 80% despite a rise in assets.
This is the first time the deficit has surpassed £300bn and is 18% bigger than 12 months ago when it stood at £255bn and the funding level was slightly higher at 83%.
On 31 May 2016 total assets were £1.2trn and liabilities stood at £1.5trn.
FTSE 100 companies recorded assets rose from 546bn in April 2016 to £552bn in May but liabilities had also risen from £640bn to £652bn.
JLT Employee Benefits director Charles Cowling (pictured) said: "Conditions are getting ever more challenging for pension schemes with prolonged low interest rates and uncertainty in the markets ahead of the EU referendum."
He also pointed towards the government's consultation on proposing to allow benefits in the British Steel Pension Scheme to be reduced, which will involve moving indexation away from the retail price index.
"The government is currently consulting on the possibility of allowing benefits to be reduced in extreme circumstances, but this is unlikely to help most hard-pressed companies which can't seem to keep deficits from spiralling despite pumping ever more cash into schemes and taking action to reduce pension risks," he added.
"There isn't too much prospect of imminent relief from markets either, as the nervousness surrounding the EU referendum is causing short-term volatility. With interest rates looking to stay low for some time yet, it seems unlikely that pension schemes will benefit from either an exit or a remain vote.
"While companies should look to continue to seek opportunities to reduce risk and settle pension liabilities, they may wish to wait until after 23 June when there may be greater clarity on the shorter term outlook for markets."
In this week's Pensions Buzz, we want to know whether you support the ruling that defined benefit (DB) trustees must equalise GMPs in past transfers.
More than £130bn of company funds are tied up in pension schemes specifically due to lower than expected levels of life expectancy improvements over the last decade, according to PwC.
Just Group has completed a £74m pensioner buy-in with the UK pension scheme of a US-listed engineering business.
XPS Pensions Group has launched a scam protection checklist to assist trustees in meeting The Pensions Regulator’s (TPR) scam pledge initiative.
Defined benefit (DB) schemes that provide GMPs must revisit and, where necessary, top-up historic cash equivalent transfer values (CETVs) that have been calculated on an unequal basis, a landmark court judgment said last week.