"We are committed to maintaining the closest possible relationship with the UK, based on shared values, and to keeping free trade as free as possible in terms of tariffs and other barriers, such as different rules," he said.

However, in a closing speech at the Portugal-Japan Investment Seminar, organised by AICEP (Portugal's Agency for Investment and Foreign Trade) in London at the Financial Times, he warned that access to the single market would not be the same.

"Any company, British or Japanese, wishing to maintain its operations in the EU internal market after `Brexit' will find a safe haven, a fertile soil, and a qualified, innovative and sophisticated destination for its business in Portugal," he promised.

According to the Prime Minister, about 100 Japanese companies operate in Portugal, employing thousands of people, referring to the establishment of the Toyota car manufacturer in 1971, but also to more recent arrivals, such as those of Fujitsu, Marubeni Corporation, Mitsui and NTT Data-Everis.

A referendum in 2016 dictated the withdrawal of the United Kingdom from the EU, but the process has been hampered by the political impasse that led to the lead of a first agreement negotiated by Theresa May's government with Brussels and the postponement of the withdrawal beyond the scheduled starting date of March 29, 2019.

Her successor, Boris Johnson, is currently campaigning for re-election and for the British parliament to approve a new agreement negotiated in October, enabling him to leave within the current deadline of 31 January 2020.