In response to questions about potential Russia-linked Twitter bot activity during the Brexit vote, Twitter provided a letter to the UK Parliament last week. The company said it had examined research on bot activity during the vote, and though many accounts it examined were sending spam, the company said it couldn’t find a link to Russian misinformation programs.

Unfortunately for the company, that answer hasn’t been enough. In a testy response sent this week, a member of Parliament asked Twitter to clarify and provide more information on the suspect accounts.

Twitter’s relationship with US lawmakers investigating Russian disinformation has at times seemed similarly strained. While Twitter, Facebook, and Google were all grilled by Congress about Russia-linked activity on their platforms, Twitter was singled out by Democratic Sen. Mark Warner, who described the company’s response as “very disappointing” and “frankly inadequate on every level.”

Twitter later failed to meet a deadline to provide Congress with more information on. Warner again said he was disappointed. “Twitter has been oftentimes the slowest to respond,” Warner said, according to The Hill. “Most of their work was derivative to the Facebook work. The other companies met the deadline which was way over a month from when they testified.”

That stressed relationship now seems to extend overseas. “I’m afraid that the failure to obtain straight answers to these questions, whatever they might be, is simply increasing concerns about these issues, rather than reassuring people,” the member of Parliament wrote this week.