The British government has said it is unable to use its £13bn aid budget to fund the hurricane rescue effort in the Caribbean since the British overseas territories affected are too wealthy to qualify for aid under official international criteria.

The criteria for overseas development assistance, enshrined in UK law, are set by the OECD thinktank and agreed to internationally. They have long been criticised by the Conservatives as too restrictive in the definition of combatting poverty.

The decision means the government will have to foot a bill that could eventually stretch to more than £100m from the general Treasury funds and not the Department for International Aid budget.

A government spokesperson said: “This is an unprecedented disaster and it was absolutely right that the UK responded immediately to the need of the people affected – this was our primary focus and continues to be our priority.

“We are looking at how the current overseas aid rules apply to disasters such as this one.”

Another official said: “These are British people on British territories and, in times of crisis, we stand by them. Absolutely nothing held us back in sending help. Our response was based on need alone.”

The news came as it was announced that the UK was to provide a further £25m aid to the hurricane-wrecked British overseas territories of Anguilla and the British Virgin Islands. Theresa May announced the extra funds as the foreign secretary, Boris Johnson, made a visit to the British Caribbean islands.

Johnson said: “It is clear this place has been through an absolutely hellish experience and there is no doubt at all that you need help with power generation, with getting the hospital back up and running, getting the airport back up and running, and schools properly set – all kinds of things need to be done.”

Johnson flew to Barbados on Tuesday before transferring to a military flight to reach Anguilla and then the BVI to inspect the scale of the damage wrought by Hurricane Irma.

Total UK aid has reached £57m, but BVI officials claim many millions more will be needed to help with reconstruction.

Political criticism mounted over the UK’s apparent indifference to the islands’ fate, especially compared with the speed and scale of the response of the French president, Emmanuel Macron. Constitutionally, the security of British overseas territories is the responsibility of the UK government.

Johnson was given a political boost when Victor Banks, the chief minister of Anguilla, said the UK government had responded within hours, but added a rider that the overall bill for the devastation caused by Hurricane Irma could top $1bn (£751m).

Banks said Johnson’s visit to the island “sends a very positive signal to Anguillians that the British are serious about their response to this very severe hurricane”.

Johnson dismissed suggestions his visit was a PR stunt, saying: “This has been long-planned ever since the hurricane broke.

“They’ve never seen anything like it for 150 years. People don’t realise that these are British people, these are British islanders and we have a duty to them.”

According to the Press Association, Johnson gave an upbeat assessment of the scale of the damage, telling a gathering at the home of the governor of Anguilla, Tim Foy, that what he had seen was very surprising.

“I had been told it was going to be a scene of devastation from the air and I have to say that I looked down as we flew in and I saw an incredible amount of tidying up had already happened,” he said.

UK officials said there was now a military presence on the BVI, Anguilla and the Turks and Caicos Islands. Seven hundred troops had been deployed as well as more than 50 police officers. More than 40 metric tonnes of aid had been distributed including shelter kits for 13,000 people.

However, HMS Ocean remained docked in Gibraltar and was not due to depart for the Caribbean for another 24 hours. Its deployment was announced on Thursday.

Billionaire businessman Sir Richard Branson, whose Necker Island retreat was devastated by the hurricane, has been in Puerto Rico helping to organise the aid response. He said he had spoken to Johnson and would be returning to the BVI.



He said: “There is an extreme sense of urgency to get food, water and aid supplies into the BVI, and we are bringing as much as we can. Once people have these, restoring order and calm to the islands will be far quicker and simpler.”

Branson said he was due to meet the deputy prime minister, Kedrick Pickering. upon arrival in the BVI, as well as the governor, Gus Jaspert. He said: “More can be done, but we are trying as hard as possible to get as much food, water and aid in as possible.”

Branson’s yacht, Necker Belle, sailed from Barbados full of supplies.

Meanwhile, BVI officials are suggesting that non-BVI residents should be evacuated from the islands since there would be no work for them in the foreseeable future.

At prime minister’s questions in Westminster, May said the emergency Cobra committee had been meeting regularly, adding: “We have now deployed over 1,000 military personnel to the region, with an additional 200 to arrive in the next few days along with over 60 police.”

The Labour leader, Jeremy Corbyn, said the UK must respond “as generously as we possibly can” to help those affected by the hurricane.

He said: “I hope that the prime minister will be prepared to look carefully at the speed of our response to Hurricane Irma and, if demands are made in the near future from any country affected by it, that Britain will respond as generously as we possibly can to help people at what must be the most catastrophic time of their lives.”

May insisted the government had reacted quickly and would be working with overseas territories on reconstruction work.