Business groups, politicians and unions have demanded Theresa May go further in spelling out the UK’s future after her major Brexit speech was described as “underwhelming”.

There was some positive reaction to the Prime Minister confirming the UK would keep current arrangements for the single market and free movement for at least two years after Brexit.

But the lack of extra detail about what kind of model the UK would seek after a transition led to concern, in particular from the UK’s private sector to call for more time to adjust.

Ms May travelled to Florence for her speech which she hoped would kick-start stalled Brexit talks, but spoke to a room made up of UK civil servants, politicians and journalists, along with some Italian officials.

Afterwards Foreign Secretary and key Brexiteer voice Boris Johnson endorsed the speech, as did Chancellor Philip Hammond, seen as the leader of those seeking a softer Brexit.

But Labour leader Jeremy Corbyn mocked the Conservatives, claiming they had adopted the position Labour set out several weeks ago on a transition period.

He said: “Fifteen months after the EU referendum the Government is still no clearer about what our long term relationship with the EU will look like.

“The only advance seems to be that the Prime Minister has listened to Labour and faced up to the reality that Britain needs a transition on the same basic terms to provide stability for businesses and workers.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

“That's because Theresa May and her Conservative cabinet colleagues are spending more time negotiating with each other rather than with the EU.”

Labour’s First Minister of Wales Carwyn Jones added that after more than a year since the referendum, “it begs the question what else could have been achieved in that period.”

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Green co-leader Caroline Lucas said: “After days of speculation Theresa May’s speech was extremely underwhelming.

“Though she has finally started to face the fact the Britain will need to contribute to EU bill in order to unlock a decent trade deal, she still hasn’t been honest about how much we’ll need to pay.

“She should be less afraid of the hardliners in her own cabinet, and more truthful to the British people.”

Prominent Brexiteer Arron Banks, the chair of Leave.EU, said Ms May had “meekly conceded” to the EU over a transition and post-Brexit payments, adding: “She has betrayed her country and the 17.4 million who voted leave – this is not what we voted for.”

Dr Adam Marshall, Director General at the British Chambers of Commerce, said the speech will be judged on whether it begins to break the stalemate in Brexit talks.

He said the constructive tone would be welcomed by firms looking for certainty as would the two year transition, but he went on.

He said: “Given the complexity of the changes ahead, a significant majority of businesses want a transition that is longer than the two years being proposed by the Prime Minister.

“We will challenge both the UK government and the European Commission over the coming months to agree a transition that lasts at least three years from the date of our formal exit from the EU, giving businesses enough time to prepare for a final deal.”

TUC General Secretary Frances O’Grady said the Government was still not being clear with the public over the trade fofs that would have to be made to secure a Brexit deal.

She said: “Reality has begun to break through into the government’s Brexit strategy, as Theresa May finally admits that a smooth transition period is desirable and necessary.

“But the Prime Minister is still pretending we can have our cake and eat it for a long-term deal.”

Sue Ferns, deputy general secretary of Prospect, the union representing more than 50,000 scientists in the UK, said: the intervention had failed to do anything to reassure the UK science community.

“Nearly 80,000 jobs rely on the UK nuclear sector, yet it was silent on the issue of Euratom and the future of nuclear co-operation,” she added.