LONDON/PARIS (Reuters) - Britain and its European Union partners clashed on Monday in a deepening row over the European Commission’s decision to exclude the United Kingdom from a new satellite navigation system, Galileo.

Britain's Foreign Secretary Boris Johnson arrives in Downing Street, in London, May 8, 2018. REUTERS/Hannah McKay

Galileo is the EU rival to the global positioning system (GPS) developed and controlled by the United States and used by millions of consumer devices globally. It was commissioned in 2003 and is due for completion by 2020.

The Commission, the EU’s executive, has started to exclude Britain and its companies from sensitive future work on Galileo ahead of the country’s exit from the bloc in a year’s time.

Britain’s foreign minister, Boris Johnson, said on Monday he had raised concerns with his French counterpart over the EU stance and the government said it might withhold security clearance for companies working on the project.

“I mentioned our slight puzzlement about what had happened with the Commission’s decision on Galileo and the satellite,” Johnson said.

“But our determination, nonetheless, (is) to go ahead with a (rival) UK satellite if that proved to be necessary.”

One expert said last week any rival British satellite navigation system could cost about 3 billion pounds ($4 billion).

A few hours after Johnson’s comments, the EU’s chief Brexit negotiator, Michel Barnier, said British companies could not be directly involved in a new EU satellite navigation system after Brexit, but Britain would have access to its signal.

“It cannot be business as usual,” Barnier said. “Third countries and their companies cannot participate in the development of security-sensitive matters.”

Asked about the issue on Monday, a French presidential adviser said there was no decision from the EU to exclude Britain from Galileo, and that the current “uncertainty” was simply the direct result of Britain’s decision to leave.

“It’s simple: Britain is part of Galileo today as an EU member, but won’t be automatically part of Galileo tomorrow as a third-party state,” he said. “That’s the mechanical, legal consequence of Brexit.”

The adviser said the issue could only be settled as part of the EU’s post-Brexit security agreement with Britain.

“In principle, the EU and France in particular have no intention of keeping Britain away or outside Galileo after Brexit, quite the contrary,” he said. “But there are ways and means in terms of access, questions in terms of security data, it’s complicated.”

The UK space agency, on behalf of the business minister Greg Clark, wrote to British companies asking them to consult the government before agreeing any new contracts to work on the project, in a move aimed at stopping the transfer of technology to EU companies.

“I regret that these steps are a necessary consequence of the position taken by the European Commission,” the letter said.