WASHINGTON — President Trump’s plans to build a border wall could cost more than three times as much as initial estimates, Senate Democrats said in a report released on Tuesday, adding that the administration has yet to provide Congress with evidence to show that a wall would be effective in stopping the flow of illegal immigration and drugs.

The report said the border wall could cost nearly $70 billion to build and $150 million a year to maintain. An internal report by the Department of Homeland Security said the wall could cost about $21.6 billion, not including maintenance.

The report, which was prepared by the Democratic staff of the Homeland Security and Governmental Affairs Committee, also found that the construction of a wall would require taking hundreds of acres of private land at a cost of millions to taxpayers and would divert money from crucial mobile video surveillance technology.

“The staff just wanted to summarize where we are at this point, given the lack of substantive answers coming from the administration,” said Drew Pusateri, a spokesman for Senator Claire McCaskill, Democrat of Missouri and ranking member on the committee.