Its emergence as the top lender demonstrates the continuing strength of the mortgage broker market - Alliance & Leicester's mortgages are only available through brokers. It also toppled HSBC, which only sells mortgages direct to consumers, which was the most competitive lender in the third quarter of 2009.
A&L received a score of 23 clearly ahead of rivals including First Direct on 19 and Woolwich on 15 in Evaluate Technologies Lender of the Quarter analysis with HSBC fourth on 14 points.
The analysis shows a return to best-buy status for nationalised lender Northern Rock as well as signs that smaller regional building societies such as Principality and Mansfield are still highly competitive despite the battering the building society sector has taken.
The independent online mortgage service ranked mortgage deals across all product categories and each time a lender appeared in the top 10 in the three months to December 31st they were awarded a point with the lender with the most points ranked as offering consistently good value.
Alliance & Leicester shot to number one despite having not featured in the top 10 in the previous three months to September 30th on the back of a strong range of products available only through intermediaries.
The analysis was notable for a number of major lenders who did not feature at all in the best buy lists including all Lloyds Banking Group lenders such as Halifax and Cheltenham & Gloucester.
Julie Speed, National Accounts Director at Evaluate Technologies said: "The changes taking place at the top of the best-buy tables indicate a good degree of competition in the mortgage market which is going to be key to supporting the property market in 2010.
"Brokers will have been particularly pleased to see Alliance & Leicester's emergence, showing that lenders value the intermediary market.
Most competitive lenders Q4
Mortgage Lender Score
Alliance & Leicester 23
First Direct 19
Woolwich 15
HSBC 14
Post Office 12
Abbey 9
Principality 9
Mansfield 8
Britannia 7
Northern Rock 5
Most competitive lenders Q3
Mortgage Lender Score
HSBC 23
RBS 18
NatWest 17
Britannia 15
Mansfield 14
First Direct 13
Abbey 10
Woolwich 8
Post Office 6
Co-Operative 5