Critics said ministers did too little, too late, despite indications that the category five storm – the most powerful ever to hit the Atlantic – would wreak devastation.
Josephine Connor, former adviser to the chief minister of Anguilla, told Sky News it had left people on the ground feeling like “third-class citizens”.
Labour leader Jeremy Corbyn also said the Government “should have acted much faster”.
British overseas territories have been battered by the deadly hurricane – with the British Virgin Islands and Anguilla suffering “severe” damage.
The Turks and Caicos Islands declared a national shutdown as they were hit in the early hours of Friday (UK time).
.As aid was being flown to the affected areas – with the first military plane to join the relief effort taking off from RAF Brize Norton – Theresa May chaired a meeting of the Government’s emergency Cobra committee.
The Prime Minister has pledged £32m towards the relief effort.
A Downing Street spokesperson said: “We believe we were swift to respond and we are getting aid to people in need.”
The Royal Navy ship Mounts Bay, which is carrying Marines, is now in Anguilla and another, HMS Ocean, is being sent to the Caribbean as part of a taskforce with several hundred troops.
However, it could take the amphibious assault ship up to 10 days to arrive.
But critics claim the Dutch and French governments, which also have Caribbean territories, were better prepared and quicker to respond.
The Dutch military had already been on the ground in St Martin for a number of hours when the hurricane hit.
Boris Johnson said “the UK Government is doing everything it possibly can to help those affected by the hurricane”.
“We’ve had a ship in the area from the beginning and as you know the PM has announced a very big aid package,” the Foreign Secretary said.
And International Development Secretary Priti Patel insisted: “It’s not right to say we have been caught out.
“The reality is we’ve had a Royal naval vessel, Mounts Bay, in the region for some time because of the hurricane and the preparedness that was taking place in anticipation of the hurricane,” she told Sky News.
“This has been a devastating hurricane, had enormous impact, it was very difficult to get supplies in because airports have been taken out, communications have been taken out.”
The Department for International Development has sent advisers to Antigua, Barbados and Jamaica to assess the damage.
But others argue the Government was too slow to act.
Mr Corbyn said the disaster was “entirely predictable”.
“The news about Hurricane Irma was well-known. The American weather forecasting system was well on top of it,” the Labour leader said.
Mrs Connor, who is in Anguilla, said: “To tell us that you’re sending us experts without a time frame and in the context where everyone knew in advance that this was going to be the largest storm ever recorded in history of the Atlantic is so unacceptable that it’s really appalling.
“We in the territories feel like third-class citizens because I’d rather wager that if there were something coming like that, of the same magnitude, to the mainland UK, I suspect that there would be far more attention being paid.”
Tourists stranded in affected regions have also complained about a lack of information and assistance from holiday companies.
Former senior Royal Navy officer, Admiral Chris Parry, said: “I think it’s a valid criticism that we knew Hurricane Irma was coming and I think contingency plans could have been a bit sharper and a bit quicker, and we could have had forces in place in order to deal with the fallout from them.”