Borrowers able to offer 10% of the value of a home as a deposit could have chosen from 779 deals at the start of March, data from Moneyfacts shows.
Six months later, the choice was now down to around 60, the financial information company said.
Lenders are being stricter about who they lend to amid fears of defaults.
Some large lenders have already said they would not currently consider applications from people on furlough and who did not have a return to work date.
First-time buyers are at particular risk from the squeeze on mortgages, as they usually have less in savings to use as a deposit.
Rachel Springall, from Moneyfacts, said the situation was "hugely frustrating" for these potential buyers.
"Product availability has plummeted since March, when there were hundreds of deals to choose from. There are now very few. Those who had expected to get a foot onto the property ladder may now hold their plans, particularly if they only have a 5% deposit," she said.
More evidenceHSBC became the latest lender to temporarily restrict lending on 90% loan-to-value deals in what one mortgage broker described as a "sign of the times".
Aaron Strutt, of Trinity Financial, said that lenders had to balance the books, and that meant a spread of borrowers ranging from first-time buyers - who might be more risky if house prices fell - to those borrowing a far smaller proportion of the value of a property.
Self-employed people were also being asked for more information, including bank statements and accounts, when they applied for a mortgage.
Mortgage lending has still picked up since lockdown, with many people trying to secure mortgages after a relatively swift agreement to buy a property during a post-lockdown pick-up in house-buying and prices.
However, there is an expectation that this mini-boom will not last as job losses mount and finances are stretched as government support schemes are wound down.