BT has said that it believes that the government will guarantee an estimated 75% of its pension fund liabilities, currently worth about £37bn.
BT has a large pension deficit
The disclosure comes amid speculation about the extent of state protection for BT's pension liabilities under the terms of its 1984 privatisation.
The "Crown Guarantee" underwrites the retirement benefits of 262,000 pensioners, should the firm collapse.
According to its most recent valuation, BT has a £2.1bn deficit on its scheme.
The Crown Guarantee will only be triggered in the unlikely event that BT is declared insolvent and its pension scheme wound up.
It applies to those members of staff and retirees who joined BT's final salary pension scheme prior to its privatisation in 1984.
However, the safety net does not apply to the 97,000 pension scheme members who joined after then.
BT closed its final salary scheme to new members in 2001. Staff who have joined the company's new defined benefits scheme since then are also not covered by the guarantee.
The existence of the guarantee - details of which only emerged earlier this month - could reduce the amount of money that BT has to make into the new Pension Protection Fund.
Under new rules, all the UK's top firms are required to pay into a government-backed fund designed to protect employee pensions in the event of company failure.
Individual company payments are currently being worked out but the guarantee means that BT's liabilities could be viewed as less high risk and thus reduce its payments.
BT said the guarantee was "an extra layer of security" for BT pensioners, most of whom no longer work for the company.
"BT stands fully behind its pension promise to pensioners and members," said chairman Sir Christopher Bland.
BT added that it would update investors about potential changes to how it funds its pension schemes in the next couple of months, after a three-year actuarial review of the schemes is completed.