A Whitehall whistleblower has lifted the lid on chaos in the immigration system, disclosing that more than one in three successful visa applications by Pakistanis “lacked credibility”.

A secret internal report, leaked to The Sunday Times by an official in the UK Border Agency, discloses how travel permits were granted without even the most basic of checks.

A Borders Agency source claimed that the report — commissioned more than two years ago — was “effectively shelved” and that the concerns raised by Chris Taylor, an official sent to Pakistan to investigate, were ignored by senior managers.

The report highlighted bogus bank accounts, letters of introduction from non-existent British companies and “tourists” who left their wives and children at home.

Up to 10,000 young Pakistanis are granted student visas each year and tens of thousands more come to Britain as tourists or business travellers.The security services believe a small minority hope to carry out terrorist attacks.

Taylor warned: “More checks and interviews could have been undertaken.” Hinting at possible corruption, he also identified some officials “who have issued more than their fair share” of suspect visas.

The Home Office insisted the immigration system had improved significantly since the damning 2006 report.

However, Chris Grayling, the shadow home secretary, described the report as “profoundly disturbing”.

“It reveals the chaos in our immigration system,” he said. “Given the much publicised terrorism issue in relation to Pakistan, it raises the question: has the government left a gaping loophole in our security?”

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