Economical with the truth
Conveying an untrue version of events by leaving out the important facts. A euphemism for lying, in short.
Recorded from the 18th century, although rarely used. It was brought into the contemporary language by the UK Cabinet Secretary, Sir Robert Armstrong, who used the phrase during the Australian 'Spycatcher' trial in 1986.
Lawyer: What is the difference between a misleading impression and a lie?
Armstrong: A lie is a straight untruth.
Lawyer: What is a misleading impression - a sort of bent untruth?
Armstrong: As one person said, it is perhaps being "economical with the truth".
What Armstrong left out (perhaps he knew but was being economical) was that the 'one person' was Edmund Burke. In 1796 Burke wrote:
"Falsehood and delusion are allowed in no case whatsoever: But, as in the exercise of all the virtues, there is an economy of truth."
In 1992, Alan Clark was cross-examined during the Matrix Churchill case and embroidered the phrase a little:
Clark: Well it's our old friend "being economical", isn't it?
Lawyer: With the truth?
Clark: With the actualité