House Speaker Nancy Pelosi on Sunday assailed the Trump administration’s efforts to block a whistleblower complaint involving President Donald Trump’s apparent effort to have Ukraine investigate former Vice President Joe Biden and his family.

In a letter to colleagues Sunday, Pelosi said the administration “will be entering a grave new chapter of lawlessness which will take us into a whole new stage of investigation” if acting Director of National Intelligence Joseph Maguire fails to provide the complaint when he testifies in front of the House Intelligence Committee on Thursday. The complaint reportedly centers around Trump’s July conversation with Ukrainian President Volodymyr Zelensky during which Trump is accused of pressuring Zelensky to investigate Biden’s son Hunter’s role at a Ukrainian energy company.

Read the rest of the story at NBC News.