HBOS, Britain's biggest lender, has made 19 changes to two-year fixed-rate mortgage deals in the past six months, research for The Times has revealed.

The bank, which owns Halifax and has a 20 per cent share of the mortgage market worth £220 billion, has changed rates almost once a week since January on the popular two-year deals, according to Moneyfacts.co.uk, the price comparison service.

Its frequent increases - and less frequent decreases - make HBOS the second most inconsistent of the UK's top 25 biggest lenders.

In the Moneyfacts list of worst performers, HBOS is second only to Leeds Building Society, which has changed its two-year fixed rate 22 times. Abbey and Lloyds TSB, the second and third-biggest lenders, follow closely behind Halifax, with 15 rate changes each so far this year.

The findings come as First Direct, the internet unit of HSBC, said that it was increasing the cost of a two-year fixed rate by 0.5 percentage points, from 5.49 per cent to 5.99 per cent. This adds an extra £46 a month on a £150,000 home loan. Nationwide, Britain's biggest building society, increased its two-year fixed rate from 6.45 per cent to 6.95 per cent this week. Woolwich, the lending arm of Barclays, withdrew all its two-year fixed-rate deals on Monday to control customer volumes.

Lenders say that the high cost of borrowing between banks has prevented them from offering better terms.

Moneyfacts found that since January, rate and arrangement fee rises have added an average £1,271 to the cost of a typical £150,000 two-year fixed-rate mortgage over the term of the deal - from £24,246 to £25,517.

The higher costs will be a blow for millions of homeowners hoping to remortgage on a two-year fixed-rate deal at the end of their current deal. In 2006, almost 1.5 million homeowners, or three quarters of all borrowers, took out fixed rates, mostly two-year deals, according to the Council of Mortgage Lenders.

Britannia Building Society was the most expensive, increasing the cost of its two-year fixed rate by £2,761 to £26,845 for a £150,000 mortgage since the beginning of the year. The rate on a two-year fixed rate from Alliance & Leicester has shot up from 5.73 per cent in January to 7.24 per cent.

Halifax has increased the rate by a smaller 0.1 percentage points, but has raised arrangement fees by £1,000, from £499 to £1,499. A spokesman for Halifax said: “We price in line with the market and in tune with any demands placed on us by the increased costs of money markets.”

Melanie Bien, director of Savills Private Finance, the independent mortgage broker, said: “The escalating cost of two-year fixed-rate mortgages is bad news for borrowers. It effectively means less choice and less flexibility as they are forced into longer fixes in order to guarantee their payments.”

Separate research published yesterday by Defaqto, the information analyst, found that the average arrangement fee on a three-year tracker rate had increased by 121 per cent since the base rate was last at5 per cent 18 months ago.

The best-performing lenders. according to Moneyfacts, include Clydesdale Bank, which charges 6.19 per cent with a £999 fee; Principality Building Society, 5.89 per cent with a £999 fee; and Skipton Building Society, 5.79 per cent deal with a £998 fee.

All change

Lender, market share and rate changes this year

HBOS20.4%19

Abbey9.4%15

Lloyds TSB8.8%15

Nationwide8.3%7

Northern Rock7.2%3

RBS 6.2%8

Woolwich/Barclays

5.7%7

HSBC Bank3.6%8

Alliance & Leicester

3.5% 9

Bradford & Bingley

2.9% 7

Source: CML, Moneyfacts

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