A dozen House Democrats are calling on Ambassador to the European Union Gordon Sondland to resign amid the developing Ukraine controversy.

Twelve representatives responded to an NBC News survey for Democratic House members by saying Sondland should resign, while others said they would wait until after he testifies on Capitol Hill on Tuesday to make a decision.

The Democratic representatives calling for his resignation are Reps. Tim Ryan (Ohio), Lloyd Doggett Lloyd Alton DoggettTrump order on drug prices faces long road to finish line Trump signs new executive order aimed at lowering drug prices Overnight Health Care: Fauci says family has faced threats | Moderna to charge to a dose for its vaccine | NYC adding checkpoints to enforce quarantine MORE (Texas), Gerry Connolly Gerald (Gerry) Edward ConnollyJudge issues nationwide injunction against Postal Service changes House panel advances bill to ban Postal Service leaders from holding political positions Shakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' MORE (Va.), Bennie Thompson (Miss.), Denny Heck Dennis (Denny) Lynn HeckExclusive: Guccifer 2.0 hacked memos expand on Pennsylvania House races Heck enjoys second political wind Incoming lawmaker feeling a bit overwhelmed MORE (Wash.), Filemon Vela Filemon Bartolome VelaHispanic Caucus asks for Department of Labor meeting on COVID in meatpacking plants The Hill's Campaign Report: Biden builds big lead in battleground Florida Texas Democrat proposes COVID-19 victims' compensation fund MORE (Texas), David Price David Eugene PriceHouse panel approves measure requiring masks on public transport Overnight Energy: 350 facilities skip reporting water pollution | Panel votes to block Trump's 'secret science' rule | Court upholds regulation boosting electric grid storage Committee votes to block Trump's 'secret science' EPA rule MORE (N.C.), Bonnie Watson Coleman Bonnie Watson ColemanDemocrats smell blood with new DHS whistleblower complaint New Jersey incumbents steamroll progressive challengers in primaries New Jersey Rep. Bonnie Watson Coleman wins Democratic primary MORE (N.J.), Anthony Brown Anthony Gregory BrownOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds Democrats push to limit transfer of military-grade gear to police Pelosi seeks to put pressure on GOP in COVID-19 relief battle MORE (Md.), Dwight Evans Dwight (Dewey) EvansWill the next coronavirus relief package leave essential workers behind? Bipartisan GROCER Act would give tax break to frontline workers Bipartisan bill aims to help smallest businesses weather the coronavirus crisis MORE (Pa.), Julia Brownley Julia Andrews BrownleyHouse Democrats eyeing much broader Phase 3 stimulus Assistant House Speaker self-quarantines out of 'abundance of caution' Actor Orlando Bloom to self-quarantine MORE (Calif.) and Gwen Moore Gwen Sophia MooreTexas Democrat: US natural gas vital in transition to renewables The Hill's Convention Report: Democratic National Convention kicks off virtually The Hill's 12:30 Report: Postal Service crisis escalates MORE (Wis.)

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“These text messages are deeply troubling. Mr. Sondland has lost credibility and must resign,” Connolly said to NBC News.

Others such as Reps. Jan Schakowsky Janice (Jan) Danoff SchakowskyAhead of a coronavirus vaccine, Mexico's drug pricing to have far-reaching impacts on Americans With Biden, advocates sense momentum for lifting abortion funding ban Hillicon Valley: Facebook removed over 22 million posts for hate speech in second quarter | Republicans introduce bill to defend universities against hackers targeting COVID-19 research | Facebook's Sandberg backs Harris as VP pick MORE (Ill.), Yvette Clarke Yvette Diane ClarkeLawmakers call for small business aid at all levels of government The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy The Hill's 12:30 Report - Presented by Facebook - Top tech executives testify in blockbuster antitrust hearing MORE (N.Y.) and Diana DeGette Diana Louise DeGetteOvernight Energy: Trump officials finalize plan to open up protected areas of Tongass to logging | Feds say offshore testing for oil can proceed despite drilling moratorium | Dems question EPA's postponement of inequality training Democrats question EPA postponement of environmental inequality training 87 lawmakers ask EPA to reverse course after rescinding methane regulations MORE (Colo.) said the ambassador should resign if the allegations are true, NBC News reported.

“If these allegations are true, anyone complicit in the president’s alleged attempts to pressure a foreign leader into interfering with our election should be removed from office immediately,” DeGette said to NBC News.

Sondland is set to appear for a scheduled House deposition Tuesday.

The whistleblower report that launched an impeachment inquiry in the House mentioned that Sondland, who was appointed by the president, tried to help urge Ukraine to investigate the president's political opponents.

The report details Trump's July phone call with the Ukrainian president asking him to "look into" former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and Biden's son.

Text messages between Sondland and top Ukrainian embassy official William Taylor made public last week show that top U.S. diplomats worked to carry out Trump's desire for the Ukrainian government to investigate the Bidens.