Failing care homes which were officially closed down have been allowed to continue operating.
The Care Quality Commission (CQC) claimed 93 homes and agencies were shut in the past year due to poor ratings.
But a BBC investigation has found a dozen were still open under the same ownership.
The CQC admitted errors, but said it was determined to clamp down on providers where there is a risk of neglect or abuse.
In some cases the regulator had allowed homes to close and then reopen on the same day, if the home applied to do so, which they can under the current rules. Damning reports about their past records were then removed from the CQC's website, so potential residents and their relatives could no longer read them.
Some of the homes said they were not even aware the regulator had placed them on an official list of providers which had closed.
The CQC announced the closures in September, saying it demonstrated a new determination to "get tougher". It said 42 providers had shut because of enforcement action, and the rest closed voluntarily after receiving poor reports.
But the BBC found some were actually allowed to remain open despite concerns about standards, while others had never been rated "poor" at all.
When reporters visited the Wykenhurst care home in Hereford, the owners admitted social services had tried to remove some of their residents last year.
Inspectors had previously expressed fears that the home was ill-equipped to deal with very frail residents, that nutritional standards were poor and that some residents were at risk of falls.
The owners of Wykenhurst pointed out that since the official closing and reopening, they had been visited more recently by inspectors who found their service to be "adequate".
The home had officially been unregistered and then re-registered on one day in November 2009. Subsequently, its previous history of poor inspection reports was wiped from the CQC's website.
To a family looking for a home for a relative, the home looked as if it was newly opened. Several other providers closed by the CQC had in fact been allowed to do the same.
Eileen Chubb, founder of the Compassion in Care charity, was the first to raise questions about the CQC's "tough" stance.
"Basically they were given a clean slate and people weren't told," she said. "That's totally wrong and totally dishonest. There's nobody out there looking for the vulnerable residents in these homes."
Amanda Sherlock, director of operations for the Care Quality Commission, admitted mistakes had been made. But she said the homes' histories should have remained on the commission's website, and promised to look into it.
"I don't think it's inaccurate that we're getting tough on poor services," she said.
"Indeed only this week we have got two organisations that are being escalated up into formal enforcement activity. There are a variety of activities and actions the CQC is following up on a daily basis."
Wykenhurst Care Home said in a statement that it had been unaware of the CQC's database error until it was informed of it by the BBC: "We explained to you that we had changed our systems to more in-depth personal care plans, as did many other homes in the last year.
"All identified previous issues raised by CQC were addressed to the satisfaction of CQC and the local authority."
The revelation comes at a turbulent time for the regulator, which was launched in April last year. In October it introduced a new, lighter-touch inspection system which it believes will allow it to focus on providers which are causing concern. There will be fewer inspections in well-run care homes where there is no cause for concern, so inspectors can concentrate on those where there may be a problem.
But charities and inspectors have claimed the system is unable to cope with such radical change.
The CQC has taken on extra responsibility for regulating health as well as social care, despite job cuts which have seen inspector numbers reduced by nearly 50% from 1400 under the old regulator - which had different responsibilities - to 800 now.
One inspector, who wished to remain anonymous, told the BBC he expected the situation to get much worse, because the remaining inspectors were due to begin regulating dentists as well. Inspectors would use self-assessment forms and other paper-based evidence rather than going out to visit providers, he said.
"As far as I'm aware there are no plans for any additional staff, so the chances of inspectors getting out on visits seem more remote than ever.
"The biggest concern for everyone is there's going to be a major incident in a home, as we're not in there as often seeing for ourselves.
"Inspectors know it's going to happen somewhere. It's inevitable something will happen which will shake the system. You just hope it isn't one of your cases."