Her admissions to the Commons home affairs select committee will raise further questions about her grip on the Home Office.
The Home Secretary has faced calls to resign over a scandal which has seen long-term residents of the United Kingdom, who came to Britain in the decades after the Second World War, wrongly stripped of benefits and threatened with deportation.
The report also said the Home Office had a process for returning families who had no legal right to remain in the United Kingdom, something which had a "single numerical target".
Comcast tops 21st Century Fox's Sky bid
The acquisition of Sky , he said, would increase the proportion of Comcast's revenues from outside the USA from 9% to 25%. That is the price Comcast said it would offer when it announced its intention to bid for Sky in February.
Rudd told a parliamentary committee she had known about the problem for months and said officials were still checking how many people had been detained over their supposed immigration status.
Rudd also rejected the claim the Home Office had targets for how many people should be deported from the country.
However, the report shows that targets for migrant removals did exist at the time and were split between regionally-based enforcement teams.
Aggressive goose takes out golfer
As the website reports, it happened shortly after Concord High School's Isaac Couling left the tee box on hole No. 7. During a recent matchup against Madison, one of the team's unidentified players was attacked by a goose.
Some said new revelations about efforts to deport people who came from the Caribbean decades ago undermined trust in British promises and so a deal to phase out EU court protection for Europeans in Britain after eight years should be reviewed.
"If there are removals targets in the Home Office and the two people who supposedly in charge don't know about them, that feels pretty serious", she said.
Labour MP Yvette Cooper MP has lashed out at Prime Minister Theresa May after the UK PM quoted her during PMQs, while trying to defend her ill-fated "hostile environment" immigration policy. Ms Rudd told MPs she bitterly regretted her failure to grasp the scale of the scandal sooner.
Jewish leaders describe Corbyn meeting as 'disappointing'
And on Thursday last week, MPs shared their own experiences of anti-Semitic threats in the House of Commons. Supporters of Corbyn have claimed the row has been stoked up by his opponents to damage him.
It was also reported today that Boris Johnson has called for May to introduce an amnesty for "squeaky clean" illegal immigrants in the wake of the Windrush scandal.