A government watchdog group has sued 12 federal agencies for allegedly withholding emails and other documents, in the latest episode in which the Obama administration is being challenged over its transparency.

The conservative-leaning Cause of Action wants the documents in order to see whether agencies are being forced to channel basic public-information requests through the White House, so that politically sensitive material can be screened. The group filed the suit Monday in a District of Columbia federal court.

The lawsuit says the agencies "stonewalled" the organization -- and claims the White House is "influencing" their response to record requests.

“Accountable and transparent government does not involve instructing agencies to send politically sensitive records to the White House for review,” said Dan Epstein, Cause of Action’s executive director.

One example cited by the group appears to show a five-month-long email exchange between Labor Department and White House lawyers over a request by the conservative Americans for Limited Government -- for the 2009 desk calendar of then-Labor Secretary Hilda Solis.

In the first days of his presidency, Obama vowed to have the “most transparent” administration in history.

However, news-gathering organizations and others seeking information on the federal government say their requests are being fulfilled less frequently.

Last month, a coalition of free press groups wrote to the White House complaining about what they described as growing censorship throughout federal agencies, adding to the growing chorus of concerns about the administration targeting reporters and restricting access.

In March, the Associated Press published a lengthy investigative report that found: "The Obama administration more often than ever censored government files or outright denied access to them last year under the U.S. Freedom of Information Act." The report also found the government in 2013 "cited national security to withhold information a record 8,496 times -- a 57 percent increase over a year earlier and more than double Obama's first year, when it cited that reason 3,658 times."

The White House, for its part, has vowed more transparency but notes it is processing information requests, declassifying records and releasing information on White House visitors

Cause of Action says its own investigations reveal the White House is “demanding” that agencies turn over congressional and Freedom of Information Act requests and related documents.

Epstein argues the manner in which the White House is asking appears like an obstruction of congressional oversight.

The Cause of Action case also focuses on a 2009 memo by then-White House counsel Greg Craig that tells federal agencies to allow White House officials to review a Freedom of Information Act request that involves “White House equities.”

Critics argue the memo effectively put tighter restrictions on information requests, as Obama was vowing to run a more open government.