"It is essential that the United Kingdom recognize the existence of the financial obligations which are simply the result of the period during which they were members of the European Union," Barnier said.
According to Barnier, Brussels and London first "have to settle the accounts of the past" in order to "start talking about the future."
Barnier said that UK financial obligations to the bloc are not "a ransom, exit bill… or punishment, as it is simply settling accounts," which will help to build the new relations in the atmosphere of trust.
UK Brexit negotiator Michel Barnier said Wednesday he would meet UK Labour party leader Jeremy Corbyn as well as first ministers of Wales and Scotland the following day.
"Tomorrow, I will meet, at their request, with Jeremy Corbyn, and also with the First Minister of Scotland, Nicola Sturgeon and the First Minister of Wales, Carwyn Jones," Barnier told reporters.
Brexit negotiations between the United Kingdom and the European Union officially kicked off on June 19, and are due to be completed by the end of March 2019.