Washington — The top Democrat on the House intelligence committee says he wants to interview the president's daughter as part of the panel's Russia investigation, along with other witnesses who Republicans aren't inviting.Rep. Adam Schiff said on Thursday that Republicans have declined to invite many witnesses that would be valuable to the probe, including Ivanka Trump and several people who he says have additional information about a June 2016 meeting between Russians and the Trump campaign."There are witnesses who have knowledge of the Trump Tower meeting and what it was about prior to the meeting that have not been brought before our committee," Schiff told reporters.At the Trump Tower meeting, several Trump campaign officials met with Russian operatives under the impression that they might receive damaging information about the Democratic presidential candidate, Hillary Clinton. The meeting has captured the interest of congressional investigators and special counsel Robert Mueller.The Los Angeles Times reported last week that Ivanka Trump talked to at least two of the meeting's participants on the way out."I think that if there's credible information that Ivanka Trump had contact with any participants in that meeting, at the time of the meeting, that she should be brought in," Schiff said. "She may have more valuable insights on a variety of other issues as well."Schiff said the committee has interviewed a total of 56 witnesses, less than half of the number of witnesses the Senate intelligence committee has interviewed in its own investigation into Russian interference and whether the Trump campaign was involved. The House interviews are done by lawmakers, and often run for much of the day. The Senate panel's interviews are done by staff.He laid the blame on House intelligence committee chairperson Devin Nunes, R-California, who stepped aside from the probe for several months while the House Ethics Committee investigated whether Nunes had at one point divulged classified information.Schiff said he and Texas Rep. Mike Conaway, who has led the probe since Nunes stepped aside, have "tried to keep the investigation on track", but "the chairman has a different agenda".Important issues to investigateNunes has been focused on a dossier of allegations about Trump's ties to Russia and whether it has been inappropriately used by the FBI. Democrats have said that's just an attempt to divert from the Russia probe.Republicans have in turn criticised Democrats for trying to draw out the probe and say there's no clear evidence of collusion between Trump and Russia. They have indicated they want the investigation to wind down in the early months of this year."The Committee is working to develop well-supported findings that will help protect the 2018 elections against hacking and other potential disruptions by foreign powers," said Jack Langer, a spokesperson for Nunes. "The Democrats, by contrast, are insisting on a ridiculous, endless investigation for public relations purposes, in order to distract from their inability to provide evidence for the wild arguments they've been making to the media all year."Schiff said there are still several important issues that Democrats want to investigate, but that Republicans won't issue subpoenas to get the information.That includes phone and messaging records surrounding the Trump Tower meeting, the White House response to that meeting, communications from WikiLeaks and records from Deutsche Bank, the German asset management firm that has loaned Trump's real estate organisation millions of dollars.The committee is expected to hear at least one witness related to the Russia probe as soon as next week: Former White House chief strategist Steve Bannon.Bannon has retained attorney William Burck for the House Intelligence Committee probe, according to a person familiar with the former White House chief strategist's decision. He has yet to be interviewed by special counsel Robert Mueller's investigators.