Millions of homeowners who use mortgage brokers are being denied access to the best deals, after a decision by some of the UK's biggest lenders to offer their top rates only to customers who approach them directly.

The banks' decision to deprive brokers of their best rates has dealt a hammer blow to the mortgage broking industry, which has lost 15 per cent of its members since the start of the credit crunch last year.

The number of mortgage advisers has fallen from about 30,000 to 26,000, according to the Association of Mortgage Intermediaries. The banks' policy of starving financial

intermediaries of the keenest mort-gages, intended to keep unwanted business at bay when lenders are struggling with funding, is expected to shrink broker numbers by a further 10 per cent.

Almost three quarters of the £15 billion in mortgages in the UK are sold through brokers, according to the Council of Mortgage Lenders (CML).

New research by Moneyfacts.co.uk conducted for The Times shows that, of the top 20 best-buy two-year deals on the market, only two are available through mortgage brokers.

The proportion of mortgage deals available through brokers has fallen by almost half in the past three months, Moneyfacts said, from 32 per cent to 17 per cent of the market.

The percentage of deals available from lenders directly over the same period has doubled, from 27 per cent to 54 per cent.

HSBC, NatWest and Royal Bank of Scotland are among the biggest lenders denying their best-buy mortgage deals to customers who arrange loans through brokers.

For instance, RBS offers a two-year fixed rate of 5.89 per cent to borrowers who approach it directly but that increases to 5.99 per cent for those who use an adviser.

Brokers have suffered as a result of the declining housing market because there are fewer buyers, despite an increase in the number of remortgaging customers through their doors.

The number of homebuyers using brokers has almost halved since the middle of last year, according to the CML.

At the same time, the number of mortgages on the market has shrunk by 54 per cent in the past six months, to 3,814, Moneyfacts.co.uk says.

This has put tremendous pressure on lenders that offer the best deals on the market, as borrowers clamour for the good rates that remain.

Darren Cook, of Moneyfacts.co.uk, said: “Banks are going direct to put a bottleneck on the market. If they offer deals directly, they can control the uptake. If they go through brokers, they can't, so they are turning off that tap. They would rather do this than pull out of the market altogether.”

Hector Sants, chief executive of the Financial Services Authority, has condoned the practice, despite concerns that it could lead to some borrowers not receiving advice about which mortgage to choose, saying: “How a lender chooses to distribute its products is entirely a matter for [it] to decide.”

David Hollingworth, of London & Country, the broker, said: “This dual-pricing is to the detriment of brokers but it is also to the detriment of consumers, pushing them away from advice and leaving them in danger of not getting the right deal for their circumstances. Brokers have helped the mortgage market move on.

No one wants to step back ten years, to when borrowers had to go face-to-face with bank staff to get a mortgage.”

A spokesman for Nationwide said: “Intermediaries can still access an extremely wide range of mortgages from Nationwide.”