Buy-to-let lending grew at more than 12 times the pace of the residential market in the first quarter of this year.
While buy-to-let grew nearly 20% year-on-year, residential lending rose just 1.6%, according to new analysis from Equifax Touchstone.
It showed total lending for the quarter stood at £36.2 billion, a year-on-year increase of 5.4%.
The average residential mortgage was £177,060, up from £170,730 in the same quarter last year.
For buy-to-let the average loan was £151,033 for buy-to-let, up from £145,017.
Equifax Touchstone data, which covers 92% of the intermediary lending market, also showed that March was the best sales month for mortgage brokers in eight years.
Lending was up 24.3% on February 2015 to hit £15 billion.
The market saw UK wide improvement with only two postcode areas, Perth and the Western Isles, reporting falls during the period.
Despite this, the number of active brokers in the market has fallen in the last 12 months, down from 8,288 in Q1 2014 to 8,028 in Q1 2015.
Market consolidation makes it even more important for mortgage providers to identify which networks and firms are leading the charge and adapting to the Mortgage Market Review, it said.
Iain Hill, relationship manager, Equifax Touchstone, said: "In March we saw lending power ahead and the sluggish trend witnessed at the end of last year has been reversed.
"There have been lingering doubts over the market recovery and it is encouraging to see such positive growth.
"While traditional savings accounts continue to offer low returns, savers are looking for alternative ways to invest their money, prompting substantial growth in the buy-to-let market.
"An oversupply of people and an undersupply of homes makes buy-to-let an attractive proposition and we expect this trend to continue to gather pace over the coming months."