"blatantly lie" is correct and usable in written English.
You can use it to describe an untruthful statement that is made openly and without any attempt to conceal it. For example: "The politicians' refusal to address the issue was a blatantly lie to the public."
"I have heard the prosecutor blatantly lie, saying, 'We found millions.' Bring the millions here".
They blatantly lie about the conditions in the detention gulags, create legal fictions to shirk our humanitarian obligations and actively try to stop medical professionals from speaking out about the sexual abuse of vulnerable people in our care.
I blatantly lie to Delaney, telling him that I wasn't thinking about the possibility of playing Duke in the second round, the team that ended our road to the championship in the Final Four last season.
They then spend endless hours on the phone with team executives and player agents, attempting to suss out the likely draft choices of each team (a process made difficult by the propensity of these sources to blatantly lie about their intentions).
Such a person will be prepared to blatantly lie in order to set up a deal.
We can't count on Microsoft and Sony to confirm anything (since deception is their natural state), and we can also ignore anything they say in the negative, since they blatantly lie about that stuff too.
"Are there any other examples of clubs so blatantly lying to their fans?
The opposition Social Democrats, who are trailing far behind Ms Merkel in the polls, accused the Chancellor of blatantly lying about Greece.
The institution of press access indeed came under attack immediately; the institution of the blatantly lying Presidential press secretary came into existence as well.
At the Beirut airport recently that meant escaping from the blatantly lying taxi drivers who tried to convince me (and almost did) that there were no buses to the Charles Helou bus station.
The experience showed that the government was as capable of blatantly lying to its people as the Soviet government before it: Just a few days before the bubble burst, President Boris Yeltsin had assured the public that the currency would never be devalued.
