Halifax, Britain’s biggest mortgage lender, will from tomorrow force borrowers with small deposits who do not use a broker to open a current account before they can get a mortgage.

The move, seen as an attempt to boost the bank’s cash deposits, will force hundreds of thousands of first-time buyers to switch their banking to the HBOS-owned lender if they want the best rates.

Halifax will also raise rates for direct business, even though the Bank of England kept interest rates on hold last week. Alliance & Leicester also raised rates on some of its deals last week.

Borrowers with a deposit of less than 10% of the value of the property will be told they have to open a High Interest current account. This requires a monthly deposit of at least £1,000.

Lenders such as Alliance & Leicester and HSBC offer preferential rates for current account customers, however Halifax has gone a step further by refusing to lend at all unless you have one.

A Halifax spokesman said: “Wholesale money continues to be significantly more expensive than a year ago. Unfortunately, this increased cost needs to be passed on to new customers.”

The High Interest account pays 5.12% on credit balances of up to £2,500, although above that the rate falls to 0.1%.

While the account has one of the highest rates on the market, experts expressed concern that borrowers who took out the Halifax mortgage would come under pressure to upgrade to expensive fee-paying accounts which generate huge revenues. Of the 1m HBOS customers who opened current accounts last year, 75% took out the Ultimate Reward account, which charges £120 a year.

Halifax has some of the best mortgage rates, and was offering a three-year fix last week at 5.74% with a fee of £999. Borrowers will not have to open a current account if they secure the mortgage through a broker – however, the rate they would pay on the above deal is higher at 6.49%.

Mortgage brokers, who normally account for 70% of all lending and are popular with borrowers who want to scour the market for the best deals, can get access to only two of the top 20 deals, according to research by data firm Moneyfacts last week.

Big lenders, including Halifax, Nationwide, and Cheltenham & Gloucester (C&G), are all bypassing brokers as part of a strategy to reduce their lending volumes during the credit crunch.

However, brokers argue it is simply a way to deter so-called “rate tarts” – borrowers who regularly switch deals at the end of the cheap initial term.

HSBC, which only offers mortgages direct to customers, has the best fixed rate and tracker deals, according to Moneyfacts. Its three-year fix at 5.53% has a fee of £999 for borrowers with a 10% deposit and its lifetime tracker at 5.63% has a fee of £599, requiring a 10% deposit. Monthly repayments would be £1,231 and £1,243 respectively on a £200,000 loan.

By comparison, the best tracker available through brokers is Alliance & Leicester’s two-year deal at 5.89%, with a whopping 2% fee and requiring a 25% deposit. This would cost you £1,275 a month – an extra £1,056 over two years, compared with going direct to HSBC.

Denise Harvey of Moneyfacts said: “It could now be argued that the best relationship you can have is with your bank manager rather than your broker.”

Brokers such as L&C Mortgages, Chase de Vere Mortgages and Charcol said they still received information about the best direct-only deals, even where they could not place business with the lender, and they would always try to inform customers about the top schemes.

However, there are fears that some smaller brokers may not adhere to such good practice.

The Association of Mortgage Intermediaries, formally complained to the Financial Services Authority, the City watchdog, last week, saying lenders were “undercutting” brokers.

David Hollingworth of L&C said drawing customers into branches with the offer of cheaper rates “risks driving borrowers into the hands of the direct salesforces offering advice on a limited range of deals at best and potentially facing tough cross-selling targets. A broker can advise the customer on whether add-ons like building insurance or packaged bank accounts are really necessary.”

HSBC offers different rates to customers who have packaged accounts, which cost £155.40 a year. HSBC’s two-year tracker for Plus accounts is at 5.88%. Standard customers pay 5.98%.

Lara Baker, 40, a town planner from Tyne and Wear, said she was refused an HSBC mortgage because she was on six months’ probation in a new job.

Baker, who had a 35% deposit for the property, worth £160,000, and ample income to cover repayments on the loan, moved from working for a council to doing a similar job at a planning consultancy.

However, broker L&C was able to get her a deal from C&G.