The European Flag waves on top of German Bundestag in Berlin | Steffi Loos/Getty Images Brexit Files Insight EU parliaments could get vote on Brexit, say German officials Even a transitional deal could affect national legislation, Bundestag analysis says.

BERLIN — Negotiating Britain's exit from the EU could be even more fraught than previously thought — because national parliaments may also be involved.

That's one of the conclusions of an analysis by the research service of the German parliament, the Bundestag, and it's backed by a senior MP in Chancellor Angela Merkel's Christian Democrats.

If the national parliaments of the 27 countries remaining in the EU — and perhaps also some regional parliaments — are all to get a say, it could make the passage of the Brexit deal more complex and leave less time for the actual negotiations.

It's generally agreed that the "divorce deal," setting out the arrangements for Britain's departure from the EU, can be sealed by Brussels and London. But Britain's new relationship with the bloc is a different matter.

The EU has suggested an initial deal would not need the approval of parliaments in member countries, as it would be only temporary — to be replaced by a more comprehensive trade agreement at a later date. The German government backs this view "with the explicit reservation that this will be reviewed at a later point in time," according to the 10-page Bundestag analysis, dated March 27 and obtained by POLITICO.

But the analysis also states that if the deal "is being ‘loaded up’ with competencies of the member states, this would turn it into a mixed agreement [affecting both EU and national legislation], which would require unanimity in the European Council and the ratification of all member states for it to be sealed, according to our current evaluation.”

Michael Stübgen, a member of parliament who chairs the EU affairs working group of Chancellor Angela Merkel’s conservative parliamentary bloc, takes the same view.

"From my understanding, we as the Bundestag will likely have to give our consent … when it comes to transitional arrangements,” said Stübgen, “which means that we will vote on it.”

Stübgen said the verdict on whether parliaments should have a vote will depend on the final shape of the transitional deal. He said he didn't expect to see any detailed drafts before the end of the year.

“Should those transitional arrangements be trivial — that means primarily technical questions — they could be implemented without a [Bundestag] vote,” Stübgen said. “However, I assume that there also will be transitional agreements that are politically highly explosive.”

This insight is from POLITICO's Brexit Files newsletter, a daily afternoon digest of the best coverage and analysis of Britain’s decision to leave the EU. Read today’s edition or subscribe here.