There have been 192 freedom of information cases which the Home Office has taken longer than a year to answer in the past three years.
In seven of these the Home Office spent more than two years dealing with the request for information.
This is revealed in material obtained by the BBC about the department's FOI performance. We received the data through an FOI application - which the Home Office took seven months to process.
The BBC's request was only answered after the Home Office was instructed to do so by the Information Commissioner, who intervened when we complained that the department had not replied.
The Home Office admits that its delay in some cases has been "unacceptable". In the past it has been censured by the Information Commissioner's Office over its slow handling of FOI applications, which the ICO has described as "extremely lengthy", "particularly severe" and "inexplicable and unjustifiable".
However Elizabeth Denham, the commissioner, faces criticism from openness campaigners for not taking stronger action over these persistent failings. The Campaign for Freedom of Information says "the ICO has been asleep on the job".
In the longest case covered by the data obtained, the Home Office replied to a request submitted on 8 September 2015 after nearly 34 months had expired, on 5 July 2018. In another it took 29 months, not answering an inquiry made in September 2015 until February 2018.
The figures also show that more than 500 requests made since the 2015 general election have taken longer than six months to be answered.
In the period covered by this data, the Home Office received a total of 9,786 FOI applications. Under the law they must be answered within 20 working days, or this can be extended for a "reasonable" period if necessary to assess whether the material is exempt from being released.
The Information Commissioner expects that all requests should normally be dealt with within 40 working days.
In a few instances the lengthy delay appears to stem from the role of special advisers.
There were nine requests where special advisers took at least a year between the case being passed to them by officials and finally clearing the response. There are 54 other examples where the special adviser stage of the process took at least six months. But this helps to explain the extreme delays in only a minority of cases.
A Home Office spokesman said: "The Home Office receives a high number of FOI requests, some complex and sensitive. The most recent published statistics show we answered 89% of non-routine requests within the deadline or with a permitted extension.
"However we acknowledge that the delay in some cases was unacceptable. We have worked with the ICO to improve the department's FOI performance. The ICO has noted that we have made and will continue to make steps to improve."
The department's poor track record has annoyed FOI activists. Maurice Frankel of the Campaign for Freedom of Information says the Home Office figures reveal "industrial scale disregard of their FOI obligations".
He said: "To have taken over two years to respond to some requests is completely off the charts. They've been allowed to get away with this for a very long time. That suggests the ICO has been asleep on the job."
The ICO states it is establishing a new dedicated compliance and monitoring department. A spokesperson said: "We recognise that many public bodies deal with sensitive issues and deciding whether to disclose is not always straightforward. That is why we work with organisations, so that their responses to requests can be given more effectively and efficiently."
"However, the Commissioner is confident that public authorities are fully aware of her enforcement powers and her commitment to exercise those powers in appropriate cases."