Savings deals are vanishing from the market at the fastest rate seen in records going back to 2007, according to a financial information website.
Some 180 deals have disappeared in the past month alone, with providers pulling deals to new savers after creeping up the "top rate" tables unexpectedly, Moneyfacts.co.uk said.
In April, 1,588 savings options, including cash Isas, were available on the market.
This was 180 accounts fewer than the 1,768 options available in March.
The fall of 180 savings options month-on-month is the biggest in Moneyfacts' records starting in February 2007.
The average rates available on easy access deals have also fallen.
Across accounts generally, the average easy access rate for someone with £5,000 to put away is now 0.51%, down from 0.56% in March.
The average easy access cash Isa on the market for someone with the same savings pot pays 0.79%, down from 0.83% in March.
The Bank of England base rate now sits at 0.1%, having been slashed twice in quick succession as part of emergency measures to cope with the economic impact of the coronavirus crisis.
The rate fell from 0.75% to 0.25% before being cut again to 0.1%.
Rachel Springall, a finance expert at Moneyfacts, said some big banks are paying rates as low as 0.01% – so savers may need to switch deals to find a reasonable return.
She also said it can take up to three months for base rate changes to be passed on to savings accounts – so worse may yet be to come in the savings market.
Ms Springall said: "Savers will be disappointed to find that deals are being pulled left, right and centre, and this vanishing act is clearly due to the base rate cuts last month and uncertainties surrounding the Covid-19 pandemic.
"Providers are perhaps struggling to sustain their lucrative offerings or are pulling deals because they have crept up the top rate tables unexpectedly, resulting in a domino effect of cuts or withdrawals."
She continued: "In light of this savings market trauma, it has never been so vital for savers to take stock of their existing account to be sure they are still earning a reasonable return.
"Switching quickly is crucial if savers want to get the most lucrative rates."