Home Secretary Theresa May has been accused of a "cover-up" after she used legal powers to keep parts of a critical inspection into UK border controls secret.
Fifteen sections of the report into controls between France and the UK have been redacted - including part of a passage revealing staff and managers fear resources in Calais are stretched - for national security reasons. But politicians and campaigners have accused Mrs May of hiding "her own failings" exposed in the report by chief inspector of borders and immigration John Vine.
Chris Bryant, shadow immigration minister, said: "Yet again the Government refuses to be straight with the British people about immigration and our borders. This cover-up and the failure at our borders provide yet more dents in this Government's much-tarnished credibility. What possible reason can there be for redacting elements of a report by a highly-respected independent inspector?
"If Theresa May thinks Mr Vine's report would imperil national security or provide ammunition for illegal migrants, she should share the full report with the Home Affairs Select Committee and ourselves and explain why the full report cannot be published without masses of redactions. This is a cover-up to hide her own failings."
In unredacted sections of the report, Mr Vine warns that thousands of illegal immigrants attempting to sneak into the UK through France have not been fingerprinted by border officials for nearly four years.
In addition, it reveals that Border Force - the Home Office law enforcement wing stationed at ports and airports - is fining drivers and firms guilty of bringing in illegal immigrants at way below the maximum allowed by law.
Mr Vine reveals that border staff remain concerned over the effect of the so-called Lille loophole, which effectively exempts some passengers who travel to Britain via Lille, in France, on Eurostar trains boarded in Brussels, Belgium, from UK Border Force immigration checks. But this section is also among those partly-redacted by the Home Secretary.
Keith Vaz, chair of the Home Affairs Select Committee, said: "I am concerned that the Home Secretary has decided to redact part of the findings related to the 'Lille Loophole', despite John Vine finding that some were still able to reach Britain using this method. The committee has been assured in the past that the loophole would be closed. The withholding of information prevents us from properly holding the Border Force to account."
Ukip leader Nigel Farage said: "It is extremely concerning that a report into the operations of our border security is being censored by the Home Office. We have to ask what on earth are they hiding? The simple fact is that the UK Border Agency is having enormous problems, not of its own making, but of its political masters, who then choose to redact the report."
Alp Mehmet, vice-chairman of campaigners Migration Watch UK, said: "Security concerns may have led to some of the redactions in the report but it is difficult to see this as the reason for all of them. Transparency has to be the best policy, if only to show that the Home Office has nothing to hide."