God said, “Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the birds of the sky, and over the cattle, and over all the earth, and over every creeping thing that creeps on the earth.” — Genesis 1:26
God created man in his own image. In God’s image he created him; male and female he created them. — Genesis 1:27
The book Jehovah of the Watchtower (by Walter Martin and Norman Klann, 1981 edition), makes the claim:
In Genesis 1:26 [KJV], Jehovah is speaking of creation, and He speaks in the plural number, “Let us create man in our image after our likeness.” Now it is obvious that God would not create man in His image and the angels’ images if He were talking to them, so He must have been addressing someone else, and who, but His Son and the Holy Spirit who are equal in substance, could He address in such familiar terms?
Many other trinitarians make similar statements. Notice, however, that it is being assumed that Jehovah could only be addressing someone who was co-equal to Jehovah. Trinitarians, especially, seem to be fond of making an assumption into the positive by using words such as ‘clearly’ and ‘obviously’, when what they are assuming is not at all clear or obvious from the scripture being referred to.
Martin and Klann, however, are trinitarians, and they simply assume that the trinity is true, and thus see trinity in scriptures where there is actually nothing in the scripture at all about a trinity. Indeed, what is truly obvious in reading Genesis 1:26,27 is that there is absolutely nothing at all in these verses about three persons in one God. The idea has to be added to and read into the verses.
The Son is not directly spoken of here. However, from other scriptures, we can ascertain that Jehovah was indeed speaking to His Son as the pre-human Logos, for the God and Father of Jesus created the world of mankind through the Logos. (John 1:3) Of course, since the Logos was the firstborn creature (Colossians 1:15), the Logos was created before the world of mankind in the image of the Creator. — John 17:1,3,5.
There is nothing in the verses that necessitates adding to the verses that the Logos had to be equal to God in order for God to address him with the term “Let us”.