"Is it a falsehood?" meaning a lie. "Do you desire gods other than Allah?" This is an interrogative phrasing, meaning: "Indeed, you have done so;" thus you worshipped them instead of Him.
﴿أئفكا﴾ كذبا ﴿آلِهَةً دُونَ اللَّهِ تُرِيدُونَ﴾ عَلَى الاسْتِفْهَامِ أَيْ قَدْ فَعَلْتُمْ؛ فعبدتموهم دونه
