The Home Office has been outsourcing immigration operations “on the cheap” because of funding shortages and a lack of interest from ministers, the government’s own chief inspector of borders has admitted.

David Bolt, who provides independent scrutiny of the UK’s border and immigration management, told The Independent that in order to “manage its capacity”, the Home Office had made subcontracting part of its “modus operandi” – and as a consequence had reduced control over its own operations.

He questioned whether there was “sufficient visibility” around the way the department had increasingly placed the onus on external agencies, such as landlords and doctors, to carry out immigration checks, and around the manner in which immigration detention, visa processing and other provisions had been outsourced to private firms.

The department has come under fire over the past year for wrongly treating those with a right to live in the UK as illegal immigrants under its hostile environment policies – an issue encapsulated by the Windrush scandal – and has been accused of creating barriers to applying for UK status through its decision to privatise the visa system.

The chief inspector said that while Home Office processes that had adequate funding and “enthusiasm” from ministers were working well, such as the EU settlement scheme, other operations were not being so effectively executed.

“The EU settlement is working better as a process,” he said. “You’ve got senior ministerial interest; you’ve got funding; the Home Office was essentially able to design the system to suit itself; you’ve got enthusiasm around delivery; you’ve got a clear target – all of those are ingredients that will make something work.

“Much of the rest of the business doesn’t feel like that. It doesn’t have clear targets; it doesn’t have the same ministerial interest; it doesn’t have the funding; and it’s not prioritised so it doesn’t necessarily have the resources, so I think that’s the department’s challenge.

“That’s why outsourcing is part of its modus operandi. That’s one way in which it can try and manage all this capacity – to give the task to somebody else.”

Mr Bolt raised concerns about difficulties for visa applicants and for other immigrants to access the services of private firms who have commercial contracts with the Home Office, such as Sopra Steria, a French firm that took over in-country visa processing in November.

The Independent revealed last month that the company had raked in millions for providing what lawyers branded a “substandard” service, which had forced some applicants to pay high fees and travel hundreds of miles to submit applications on time.

MPs and lawyers subsequently called for an independent investigation into the outsourced system, raising “extreme concerns” about Sopra Steria’s “capacity and ability” to run the service.

Speaking after an event organised by the All-Party Parliamentary Group for Visas and Immigration on Thursday, Mr Bolt said: “When you hear that people have difficulty accessing Sopra Steria or any of the other outsourced commercial contracts, what is the Home Office doing to ensure that what they’re providing is actually meeting the terms of the contract?

“In earlier contracts, one of the challenges was whether the contract had been properly funded, so there’s been an attempt to try and do things slightly on the cheap. And then it always feels rather reluctant to press the provider, because they realised they’ve got the provider over a barrel.

“The question is, does it retain sufficient visibility of what’s going on and sufficient control over it? And to what extent is it accountable for what’s delivered?”

He also said that when the department placed requirements on agencies such as the NHS, schools and landlords to carry out immigration checks as part of its hostile environment measures, he was “not sure that it [took] enough responsibility for what then happens”.

A report published by Mr Bolt in 2016, which aimed to understand how the Home Office was going to assess the effectiveness of the hostile environment policies, found there were “no real measurements in place to collect, analyse and evaluate” the measures.

But the chief inspector questioned whether the department had “the capacity to do anything about it” because they were “short of resource generally, meaning everything is under pressure” – likening the situation to “changing a tyre as you’re driving down the motorway”.

“Across all of the Home Office, its business is bigger than its capacity to manage. It’s constantly having to make decisions about priorities, and getting dragged off to do things. That for me is one of the key issues – whether it’s got the bandwidth to cope with everything,” he added.

A Home Office spokesperson said: “We welcome the independent scrutiny of the chief inspector and take his comments, criticism and recommendations very seriously.