The body that represents NHS trusts says a lack of testing could have meant some patients with COVID-19 were discharged from hospitals into care homes.
NHS Providers denied that trusts knowingly moved patients with the coronavirus into social care.
But the group's chief executive, Chris Hopson, said hospitals were only asked to "systematically test every single patient due for discharge to social care" on 15 April - after the peak of the virus had hit.
Mr Hopson said this meant it was possible "that a very small number of asymptomatic COVID-19 patients, who trusts were unable to test prior to that date, were discharged to social care".
Sky News has reported extensively on the situation in care homes throughout the coronavirus pandemic.
This includes highlighting fears elderly patients were being discharged from hospital before they were well enough to return, as well as reporting that a number of councils threatening to withhold funding to help care homes deal with the virus if they did not agree to take in COVID-19 patients.
Boris Johnson yesterday said there was a system of testing in place for patients going from hospitals to social care and pledged a further £600m for infection control in care homes.
Speaking to Kay Burley@Breakfast, Health Minister Edward Argar said the suggestion that care homes had been "abandoned" or "deprioritised" was "completely wrong".
But Mr Argar did say that initially testing was focused on "frontline NHS staff to make sure the NHS was there to care for people".
"You're right to talk about… mid-April, when the capacity was there in the testing system to make sure that those going into care homes could be tested and indeed all care home staff," said the minister.
Former health secretary Jeremy Hunt said it was "very clear" that testing for COVID-19 should have been ramped up earlier.
Speaking to the same programme, he said: "That led to one of the issues that's affected care homes, which is people being discharged from hospital without being tested for COVID.
"Anyone who had symptoms wouldn't have been discharged from hospital, but we know that around half of the shedding of the virus happens before people have symptoms.
"Now we've ramped up the testing capability, we're able to address those problems."
Labour has called for the prime minister to account for official figures showing 10,000 "unexplained" excess deaths in care homes last month.
The party's shadow social care minister Liz Kendall said the government needed to "get a grip of this crisis, implement a full strategy for supporting care homes, and give all social care services the priority and resources they deserve".
Speaking to Sky News, shadow communities and local government secretary Steve Reed said the situation in care homes was "intolerable".
He said councils are facing a "£10bn black hole" because of COVID-19 and this could mean billions will be cut from adult social care unless ministers step in.
Niall Dickson, chief executive of the NHS Confederation, which represents organisations across the healthcare sector, said care homes are where the "major battle with COVID-19 is now raging" and the sector had been "neglected" for too long.
"When this is over, it will be time to tackle our collective failure to address social care, which is nothing short of a national disgrace", said Mr Dickson.
Mr Hopson said any public inquiry "will need to look at the role that the lack of testing capacity and PPE has played in the high number of care home deaths".
He added that "the scandal here is the repeated failure of politicians to solve our long running social care crisis".
The PM's spokesperson said yesterday there is a "regime in place that people being discharged from hospital are being tested and care homes have clear guidance to say they should take all necessary precautions against the spread of coronavirus in their premises".