Former Conservative leader Iain Duncan Smith has hailed Theresa May for her “upbeat” Brexit speech in Florence, saying the Prime Minister confirmed that Britain’s era in the European Union “will soon be over for good”.

His comments came as Mrs May laid out more details of Britain’s withdrawal plans in an address to EU nations, including a two-year transition period after the UK exits in 2019.

Writing in the Daily Telegraph, Mr Duncan Smith said: “She confirmed that we will indeed leave the single market, escape the jurisdiction of the European Court of Justice (ECJ), and have control again of our own laws and regulations.

Theresa May delivers a speech in Florence. (Jeff J Mitchell/PA)Theresa May delivers a speech in Florence. (Jeff J Mitchell/PA)

“She confirmed, too, that freedom of movement would end.

“The most powerful part was her upbeat statement that leaving the EU will be good for us – a stark contrast to the rampant negativity of those who spend their whole time wishing we weren’t leaving.”

In the keynote speech in Italy, Mrs May proposed the UK could pay around £18 billion into the EU budget during an “implementation period” lasting until 2021, during which “the existing structure of EU rules and regulations” would continue – and people from the EU would be able to move to the UK under a registration scheme.

A leading advocate of Brexit, Mr Duncan Smith admitted the “implementation period” would be controversial, but said: “I took from her words that this will not entail staying in the single market, nor staying under the jurisdiction of the ECJ” – policies he said he had “fought tooth and nail against” for years.

“It must reserve us the right to negotiate with other countries, to adjust our laws as we see necessary, and set such limits on freedom of movement as we see fit,” he said.

The Tory MP added he believed the overall message from the Prime Minister was that in two years’ time, “Britain will once again be a sovereign state”.