Galileo, a rival to the US-owned global positioning service, became a flashpoint in Brexit talks last month after London accused the EU of shutting out British companies from the project.
Britain’s Brexit Secretary David Davis said this month that Britain had been instrumental in developing Galileo’s technology, and blocking it at this stage would delay the project by up to three years and increase the bill by £1billion ($ 1.2 billion).
Mr Barnier told reporters, referring to the Galileo Public Regulated Service: “The rules as they are today, a third country cannot take part in the development of the PRS signal.”
Britain was among the 28 member European Union member states to approve the rules, he added.
Barnier told reporters on the sidelines of a conference in Vienna: “There is a way for the UK to be included in a partnership about Galileo as a user of (services) including the PRS.”
He added the issue should be addressed “in the framework of our future strategic partnership with the UK”.
When asked if that meant Britain could not take part in the project’s development, however, he said: “Not development. It is a unanimous decision of the 28. “The facts have consequences.”
The row over acces to Galileo has been brewing for weeks.
Mr Barnier has previously been clear the UK would lose access to Galileo’s PRS service – an encrypted service used by EU member states’ militaries and emergency services.
Theresa May blasted the EU has been taking Britain “for a fool” over the situation.
Speaking to Andrew Marr at the weekend, the Prime Mnister said: “Let’s just look at Galileo. The UK has been contributing significantly to the Galileo programme so far
“Yes, the EU are saying that in the future, they don’t think that not as a member of the EU, we will be able to continue to contribute and have the access as a member of the EU.
“We are still discussing that with them. What we as a Government have said is that if that is your decision we will ensure that Britain has what Britain needs, and we will do it ourselves.”
British firms will still be unable to work on Galileo’s development after Brexit with European Space Agency delegates voting to maneuver around UK attempts to halt the project’s next round of satellites.
Britain had hoped to delay the next round of contracts for the project after the country’s firms were blocked from bidding on Galileo contracts in the hope negotiations would move on to allow British involvement.
However, EU member states have ganged up on Britain and voted to give the go-ahead for the next set of satellites in the bloc’s joint navigational system.