Of American-English origin, the phrase inoperative statement is a euphemism for a lie.

For example, the following is from Trump is the Picasso of hogwash, by the U.S. political satirist Will Durst (born 1952), published in the Baxter Bulletin (Mountain Home, Arkansas) of 21^st March 2017:

The English language has a healthy share of euphemisms for lying. Fabrication. Falsification. Making stuff up. Inoperative statements. Alternative facts. Big fat fibs. Untruths. Puffery. Flummery. Fast food advertising. NFL owner profit/loss statements.
But they all mean the same thing: saying out loud things you know are not true. No matter which polite term you prefer, America is in the middle of a lying renaissance. And we have President Donald J. Trump * to thank for perfecting the practice of public prevarication to an art form. He is the Picasso of hogwash.

(* Donald John Trump (born 1946) has been the 45^th President of the USA since 20^th January 2017.)

The phrase inoperative statement was coined by Ronald Lewis Ziegler (1939-2003), who, from 20^th January 1969 to 9^th August 1974, was the White House Press Secretary under President Richard Nixon.

(The Republican statesman Richard Milhous Nixon (1913-1994) was the 37^th President of the United States from 20^th January 1969 to 9^th August 1974. He resigned from office, owing to his involvement in the Watergate scandal.)

The following explanations are from the obituary of Ron Ziegler, by Harold Jackson, published in The Guardian (London and Manchester, England) of 12^th February 2003:

During his career as US President Richard Nixon’s press secretary, Ron Ziegler, who has died after a heart attack aged 63, delivered thousands of White House statements. But the only one that reverberates down the years came on April 17 1973, and consisted of two short sentences: “This is the operative statement. The others are inoperative.”
This pronouncement signalled the first breach in the wall of lies and evasions that the Nixon administration had erected around the break-in at the Watergate headquarters of the Democratic national committee in June 1972. After months of press revelations and congressional investigation of official corruption, the president had finally given in, ordering his staff to give evidence to the US senate and lifting their immunity from prosecution. In response, his press secretary simply junked all his previous statements on the issue.

These are Ziegler’s exact words—according to The Sun (Baltimore, Maryland) of 18^th April 1973:

Ziegler explains

Washington Bureau of the Sun
Washington—The presidential press secretary, Ronald L. Ziegler, was asked several times yesterday about the relation between past statements made by the President and spokesmen for the White House on the Watergate investigation denying any involvement of staff aides. He explained:
“The other statements that were made were based on information that was provided prior to these events, which have been referred to in the President’s statement today [yesterday]. Therefore any comment which was made up until today, or previously, was based on that activity. This is the operative statement.
“The way to assess the previous comments is to assess it on the basis that they were made on the information available at that time. The President refers to the fact that there is new material. Therefore this is the operative statement. The others are inoperative.”

The earliest occurrence that I have found of inoperative statement used as a phrase, i.e., without explicit reference to its origin, is from the column About People, published in The Sacramento Bee (Sacramento, California) of 14^th May 1973:

Nosey Puppet

Richard Goore, 2, son of Mr. and Mrs. Kenneth Goore of Sacramento looks in wonder at Pinocchio’s nose, as the proboscis grows with each of the puppet’s “inoperative” statements. Pulling the strings is Angela, the Puppet Lady, Mrs. Lee Canright of Pollock Pines. She performed at the Woodlake Inn for Mothers’ Day.

The second-earliest occurrence that I have found of inoperative statement used as a phrase is from the column Friday finishers, published in the Billings Gazette (Billings, Montana) of 22^nd June 1973:

Sure thing

Backers of gambling for Montana have misspoken themselves with an inoperative statement.
We refer to those who call slot machines gambling. Uh uh, in no way.
Those one-armed bandits, why the only way to beat them over the long pull is to put them in a wheel barrow and take them to a sledge hammer party.
That’s a winner every time!