About 100,000 Latvians are living in the UK, according to British estimates, while Latvia's Foreign Ministry puts the number at up to 150,000 said Rinkēvičs.
"Neither we, nor Britain have exact data as no one is obliged to register there," said Rinkēvičs.
He said that one of the main talking points with British officials were the fates of Latvians living in the UK following Britain's exit from the EU in 2019. While it isn't happening en masse, Latvian officials are also receiving complaints from Latvians living in the UK.
"We have information that people have been offended [because they're immigrants], however we notified the British Foreign Ministry about that. [..]," said Rinkēvičs.
"There were cases when municipalities asked people to sign some papers. They knew little English but the documents said they have to leave the country. This is against the laws of both Britain and the EU, of which the United Kingdom is still a member," he said.
Currently the Foreign Ministry is working on that the status of Latvians living in the UK wouldn't change after it leaves the EU.
"We think that the same should apply towards British citizens. But there's the distinction that a lot depends on the talks between Britain and the UK. Many elderly Brits are living in Spain, Portugal and other southern countries of the EU," said Rinkēvičs.
"They are using local medical services and social welfare. For example, Spain has a question of who'll be paying for that after 2019. [..] In the current case we're helping to form the common view of the EU over the matter. However if the treaty doesn't seem right to us, we will not agree to it," said Rinkēvičs.
Latvia's Foreign Minister also used the interview to suggest Europe should be made less federal.
"We're interested for the EU to be a union of powerful national countries. And it is my view that sometimes we've exaggerated the federalization of several matters and we shouldn't take further steps in this direction," said Rinkēvičs.
The powers of Brussels should be cut, giving more leeway to national governments, said Rinkēvičs.
"It could help save the EU. I don't know what will happen 20 to 30 years from now, but our current task is saving the EU," he said.