Repayments on tracker rate mortgages will automatically fall
Lenders "will not rush" to announce a drop in the cost of variable rate mortgages after the Bank of England slashed interest rates to 3%.
Michael Coogan, of the Council of Mortgage Lenders, said lenders would take their time given the hefty cut.
Meanwhile, major lenders have withdrawn tracker rate deals for new borrowers as they wait to see how the industry reacts to the cut.
The Chancellor has repeated calls for banks to pass on interest rate cuts.
Alistair Darling backed up earlier comments from Prime Minister Gordon Brown for the banks to help individuals and small businesses.
"I think it's essential that the banks do pass on the benefit of lower interest rates to people and to businesses," Mr Darling said.
"Banks need to understand that they need to help their customers."
Before the announcement some lenders suggested they would pass on the cut in full to standard variable rate mortgage deals - around 10% of total home loans.
Meanwhile, savers are likely to face a cut in the interest rates they receive from their deposits.
Existing customers with tracker rate mortgages - with repayments that fall or rise in line with the Bank rate - will automatically feel the benefit from the latest cut, primarily from 1 December.
According to price comparison website Uswitch.com, a customer with a 25-year £150,000 mortgage on an average two-year tracker rate of 6.27% will see their monthly repayments fall by £134 to £856.
But existing customers with fixed-rate deals will pay the same amount as they have been until their term comes to an end.
About 50% of existing mortgages are fixed rate deals, 40% are tracker rates and 10% are variable rates.
New customers will have to wait to see whether the Bank rate change affects the cost of new home loans.
Even before the change Lloyds TSB/Cheltenham and Gloucester announced that they would pass the cut on in full to Standard Variable Rate (SVR) customers.
Since the decision, major lenders such as HBOS, Abbey, Alliance and Leicester, Barclays and HSBC have said their variable rates are "under review".
Nationwide, the UK's biggest building society, said it was "monitoring the markets" before making a decision.
Michael Coogan, director general of the Council of Mortgage Lenders, said he expected there to be "no rush" by lenders making announcements about rate cuts on Thursday.
He told the BBC that the cut was good news for consumer confidence, but it would need to be fed through to interbank lending before mortgage customers felt the benefit.
The key to mortgage costs is Libor - the London Interbank Offered Rate - as this is the rate that banks lend to each other.
"This will be a key figure to watch in terms of assessing how much of the cut is likely to be passed on in rates offered on new tracker mortgages and in lenders' SVRs," said Ray Boulger, of mortgage brokers John Charcol.
"However, as with last month, I expect only a small minority of lenders to cut their SVR by the full amount."
He warned that even existing tracker rate customers might not see any further reductions if the Bank rate is cut again in future months, as a 3% floor is written into some deals.
Major lenders have been pulling nearly all tracker deals for new customers from the market after the Bank rate cut.
These are expected to be re-priced and put back on offer when lenders gauge the level of Libor on Friday.