A Government minister has denied that the UK is outsourcing its responsibilities by sending migrants to Rwanda, after religious leaders criticised the move.

Greg Hands also echoed Home Secretary Priti Patel’s challenge for critics of the plan to come up with a better idea to tackle small boat crossings.

Ministers are facing mounting anger over the policy from across the political spectrum, with veteran Tory MP Sir Roger Gale accusing the Government of shipping people abroad like “waste”.

It comes after the Archbishop of Canterbury, Justin Welby, said the UK is “subcontracting out our responsibilities” by sending migrants thousands of miles to east Africa, which he claimed is “the opposite of the nature of God who himself took responsibility for our failures”.

Dr Rowan Williams, a former archbishop of Canterbury, backed his successor in condemning the move on Monday, saying it is “not in accord with what I understand about God”.

He told Times Radio: “Is the policy sinful? I think, in a word, yes. I think that without commenting on the motivation or moral standing of any individual involved, the policy itself seems to me to be not in accord with what I understand about God.”

Put to him that the UK was “outsourcing” its responsibilities, energy minister Mr Hands told Sky News: “No, we’re not. This is an agreement between two sovereign countries, the UK and Rwanda.

“I think what others, the critics of this plan, need to do is to show what their solution would be.”

Ms Patel had challenged opponents of the scheme to come up with a better idea to tackle “illegal” migrant crossings.

On Sunday, the Archbishop of Canterbury was joined in his criticism of the policy by the Archbishop of York, Stephen Cottrell, who said: “We can do better than this.”

But writing a joint article in The Times with Rwandan foreign minister Vincent Biruta, the Home Secretary insisted her controversial plans were “bold and innovative”.

She added: “It’s surprising that those institutions that criticise the plans fail to offer their own solutions.”

Speaking to the PA news agency on Monday, Sir Roger said he is “gravely concerned” about the policy.

“I’m likely to be in a tiny minority within the Conservative Party, I suspect, but I am gravely concerned about the ethics, the morality, the legality and, brutally, also the cost effectiveness of what she is proposing,” he said.

Sir Roger said he does not have a “bright idea” for an alternative but there must be an “international solution” to the problem.

“My personal view is that this is a superficial scheme that almost certainly won’t get off the ground,” he said.

He added: “There was a time when we used to ship our waste to other countries – China and all sorts of places, I think – for processing. I mean, literally our garbage.

“It’s almost like that – well, we don’t want this problem, so we’ll pay somebody else to deal with it.”

Sir Roger said that while he may not know how to solve the problem, “we need an answer – but we need the right answer, and I don’t think this is it”.

Meanwhile, more people were seen arriving in the UK in small boats on Monday.

Earlier, Mr Hands said sending migrants to Rwanda will act as a “significant deterrent” to people deemed to be entering the UK illegally.

Asked when he expects to see the results of the policy, amid suggestions even within the Home Office that it will not work, he told Times Radio: “We think that it will work and we are confident that it will work.

“We need to be sending that message now – that crossing the Channel illegally isn’t necessarily going to lead to the person being located in the UK.

“So the relocation to Rwanda is there – it will act as a significant deterrent, we think, to people making that journey. And (it) will ultimately be at the cost of the people smugglers who… we want to put out of business.”

An exchange of letters published by the Home Office on Saturday night showed the department’s permanent secretary Matthew Rycroft warned Ms Patel that although the policy was “regular, proper and feasible”, there was “uncertainty surrounding the value for money of the proposal”.

Issuing a rare ministerial direction compelling the plans to go ahead despite the concern, the Home Secretary said: “Without action, costs will continue to rise, lives will continue to be lost.”

Shadow policing minister Sarah Jones said it is “madness” to expect migrants to stay in Rwanda after they try to reach the UK.

She claimed the Government is merely “moving” the people-smuggling problem rather than “fixing” it.

Speaking to Times Radio, she said: “The Government hasn’t even said how much this is going to cost – the £120 million is just an upfront payment to the Rwandan government. The actual admin of the scheme, they don’t even know how much that’s going to cost.

“Sending people 4,000 miles before they’ve made a claim and expecting them to stay in a country they don’t want to be in is madness.

“We are just moving the people-smuggling problem, we are not fixing it, which is what the Government claims to try and do.”

A Home Office spokesperson said: “This world-leading migration partnership will overhaul our broken asylum system, which is currently costing the UK taxpayer £1.5 billion a year – the highest amount in two decades.

“It means those arriving dangerously, illegally or unnecessarily can be relocated to have their asylum claims considered and, if recognised as refugees, build their lives there.

“There is nothing in the UN Refugee Convention which prevents removal to a safe country. Under this agreement, Rwanda will process claims in accordance with national and international human rights laws.”