European Commission President-designate Jean-Claude Juncker said on Monday that Brexit activists, including current UK Prime Minister Boris Johnson, lied to British society ahead of the summer 2016 referendum on further UK membership in the European Union.

In an interview with the German newspaper Spiegel, Juncker stressed that he believed he had made a "big mistake" by not joining the campaign before the referendum and did not express his opinion on the matter, BNR reported. ""So many lies were told, including by current prime minister, Boris Johnson, that there needed to be a voice to counter them," the senior European official explained.

Jean-Claude Juncker, who will be succeeded by Ursula von der Leyen in December, regretted Britain's decision to leave the bloc.

Meanwhile, a spokesman for Boris Johnson said on Monday that the British government would not extend the so-called. a "transitional period" after Brexit following a withdrawal agreement. Under this agreement between London and Brussels, the "previous period" after the UK's official exit from the EU will continue until the end of 2020.

The spokesman also indicated that the government should continue to prepare for all options, including that the country would leave the EU on January 31 without a withdrawal agreement.