As a result of the increase, the total number of completions reached 2,500 last month.
Second charge lending dropped by 18% between November and December 2021, according to data collected by Loans Warehouse.
As a result of the increase, the total number of completions reached 2,500 last month.
Lending totalled £118.4m in December, representing an £18.6m decrease on November 2021.
Average completion times were at 23 days, 0.4 days slower than the month before.
The majority of products were provided under 85% loan-to-value (LTV) at 84.16%.
The most popular reason for taking out a loan was consolidation and home improvements (40), followed by consolidation (36.8%).
Matt Tristram, managing director of Loans Warehouse, said: "The figures reported directly to Loans Warehouse from second charge lenders confirm lending totalled £118.4m in December 2021.
"Whilst the number of completed loans reduced to 2,500, the average loan size exceeded November's record breaking £45,399, rising to £47,394.
"The figure represents a 76% increase on December 2020 and the continuation of a boom in second charge lending that hasn't been seen since before the Credit Crunch, let alone the pandemic.
"In fact, we can confirm that Q4 2021 is the highest recorded lending since Q4 2008.
"December's figures take the total lending for 2021 to £1.180bn from over 27,000 loans completed in the last 12 months.
"In a rare event for the festive period, which further demonstrates how quickly second charge lending is growing, December even saw one lender report record completion figures.
"In other news, we start 2022 with the industries biggest lender, Optimum Credit, rebranding to Pepper Money from 24th January, after purchase in October 2018."
