Professionals will be able to borrow against their bonuses, as well as regular income, said Investec Specialist Private Bank, which is launching the scheme.
The mortgages will only be offered to people borrowing in excess of £1m.
The Centre for Economics and Business Research (CEBR) estimated earlier this year that bonuses would be around £7bn. But recently it has become likely that this figure will come in lower as many banks increase salaries rather than bonuses.
Three quarters of City workers expect their bonuses to be higher than last year, Investec said.
House prices have tumbled this year, falling for the fifth consecutive month in November, according to property website Hometrack.
Meanwhile the Bank of England reported an eight-month low in mortgage approvals in October.
Tight credit conditions are dragging the market down despite positive economic growth, say analysts.
Wealthy cash buyers, who can avoid credit difficulties, have kept prices afloat in London.
And they can now be joined by high earning counterparts borrowing against their assets, said Jack Jones of Investec.