A tourist carrying a Union Flag umbrella walks in the rain during a spell of wet weather, next to The Tower of London, in London, Britain January 15, 2017. REUTERS/Peter Nicholls

BRUSSELS (Reuters) - The European Ombudsman called on the EU’s Brexit negotiators on Thursday to give the public access to documents and accept their input during the talks on Britain’s withdrawal, which are due to start in the coming weeks.

Emily O’Reilly, who as Ombudsman has power to investigate complaints from the public about the EU authorities, wrote to European Commission President Jean-Claude Juncker asking for assurances the EU executive would share information during the two-year process, especially as it concerns citizens’ rights.

Her office, she said, had already had complaints from people seeking clarity on how Brexit will affect them. Firms trading between Britain and the continent, EU citizens living in Britain and Britons living in continental Europe face uncertainty.

Acknowledging a need for some confidentiality, O’Reilly, an Irish former journalist, said: “It would be helpful to ... give citizens access to relevant information and documents at the appropriate time and without the need to ask for them.”

British Prime Minister Theresa May is expected to trigger the exit process later this month under Article 50 of the EU treaty. Preparations on both sides have been marked by secrecy and conflicting demands. EU officials are particularly anxious to prevent London sowing division among the 27 other EU states.

In other EU negotiations, notably over a controversial free trade pact with the United States, the Commission has yielded to calls from campaigners to publish some documents in a bid to ally public suspicion of what was under discussion.

In a tweet, Juncker’s chief Brexit negotiator Michel Barnier said on Thursday: “Transparency and democracy (are) essential for success.” His comment came after a meeting with the speaker of the European Parliament, which must endorse any Brexit deal.