A family who endured a "living nightmare" at the hands of a violent criminal will receive a £130,000 payout from the Home Office after its failings put their lives at risk.
Officials failed to stop the overseas offender returning to Britain and the man went on to wage a campaign of terror against the family, an investigation by the Parliamentary and Health Service Ombudsman found.
The Canadian man had lied about his criminal record when he came to the UK but the mother of a woman he lived with became suspicious about him and paid a private investigator to look into his past.
She contacted the Home Office when it emerged he had an extensive history of violence and gave them details of a flight he was taking back to Britain after a holiday, but he was never picked up - despite lying on a visa application being grounds to refuse a person entry for ten years.
The man went on to harass the family with repeated texts, emails and telephone calls and was arrested several times. On one occasion the police found him test firing a crossbow and an air rifle and discovered he had bought a white van that he had converted to replace the rear windscreen with a metal grill.
Police informed the Home Office about the offences but were told the man had permission to be in the UK so was not of interest to them. The department also lost two further letters it received from the family setting out their fears about the offender.
In the damning report, the ombudsman found that the Home Office did not listen to the family's concerns and continually failed to put right their earlier mistakes, causing them u nnecessary pain and distress.
Ombudsman Julie Mellor said: " A mother and her family were forced to endure a living nightmare for months on end because of the Home Office's repeated mistakes.
" Vital opportunities to protect the family were missed because procedures weren't followed, allegations weren't followed up and two of the complainant's letters lost.
"The Home Office needs to embed a culture of learning from mistakes into the organisation to ensure that no one else goes through this terrifying experience. We are pleased that the permanent secretary will be taking responsibility for looking at their systems and processes to ensure this never happens again."
When the daughter's relationship broke down with the man at the end of 2010 he began to send anonymous letters about the family to employers and neighbours containing serious allegations and made repeated telephone calls.
He was a rrested for harassment, theft and criminal damage in March 2011 and bailed on condition he did not go near their home.
The following month he was arrested when police found him test firing a crossbow and days later, after neighbours discovered a fire at the family's house, the man was arrested again.
According to the ombudsman the events leading to his arrest "would not have happened without the Home Office's serious mistakes".
Those errors made it " harder" for the family to protect themselves and that has had a "lasting, negative, effect on the family's emotional capital and their physical and mental resilience", the report found.
The ombudsman said the Home Office did not have adequate measures in place to test information about visa history, criminal convictions and good character. Officials who rule on applications check only UK databases and i nformation about criminal offences committed outside the UK is not generally available, the report said.
It has called on the department to pay the family £120,000 as an apology for its mistakes and £10,184 towards expenses as well as hold reviews into visa checks, how allegations are handled and the way correspondence is dealt with.
Home Affairs select committee chairman Keith Vaz said: "This is a damning report. The Home Office will now have to pay compensation, funded by the taxpayer, of £120,000 which could have been used to employ five immigration officers.
"E ffective enforcement is a key issue for the Home Office and they should act on the type of information provided in this case immediately.
"Allegations made by the public need to be treated with respect. A lot has been said by ministers about the need to remove those who offend but this is an example of an offender being allowed to enter the country only to go on to re-offend.
"We must ensure that these types of cases are never repeated."