A hastily buried official report has estimated that the government is spending an extra £6bn a year protecting pensioners' incomes, deVere Group understands.
The report also warns that the cost of doing so in future years could spiral further.
The warning came in a report from the Government Actuary's Department, which was published last week on the government website but was removed a day later; an official said it had been published "in error".
The triple lock was introduced in 2011 with memories of the row over Labour's 75p pension increase in 1999 still fresh in the memory.
Official figures on Tuesday confirmed that benefit payments and pensions for millions of retired