Suspicion was voiced by EU sources who told The Telegraph newspaper that the British had obtained sensitive documents intended for EU officials "within hours" after they were unveiled.
The documents, circulated in July, reportedly contained harsh criticism of the UK’s plans to stay in the EU single market.
Spying among allies was rejected as unacceptable by German Chancellor Angela Merkel after whistleblower Edward Snowden’s leaks revealed the United States had wiretapped her cell phone. But sources have told the paper the incident was a wake-up call for the union.
The United Kingdom voted to leave the European Union in June 2016, with the negotiations between the two parties expected to last until March 29, 2019.
According to a recent poll conducted by Sky Data on July 20-23 among 1,466 people, 51 percent of respondents believe that Brexit will be "actively bad" for the country, and 50 percent welcome the idea of holding another referendum.