Ms Davidson was questioned on whether the 13 Scottish Conservative MPs will vote with Theresa May on amendments to trade legislation, after three joined pro-Brexit MPs in a written demand for a clean break with the EU.
Pushed to guarantee the vote, on the BBC’s Good Morning Scotland programme, Ms Davidson said: “We will support her if she fulfils her principles, which I expect her to do.”
Her comments follow Scottish Conservative MPs Alister Jack, Stephen Kerr and Colin Clark joining 62 UK Conservative colleagues in signing a letter to the Prime Minister calling for full regulatory autonomy after Brexit with no prevention of trade deal negotiations with other countries.
Ms Davidson then outlined the principles, saying: “As we leave the European Union we do so as a stronger country without leaving one part behind as was suggested by the EU today in terms of Northern Ireland, I think that is completely unacceptable.”
Further principles were to maximise trade and ensure there is no hard border between the Republic and Northern Ireland.
She said she expected the Prime Minister to “push back” on the Irish question in her key Brexit speech on Friday.
She said she hoped the speech would move the Brexit process on and said a customs union is one way of dealing with the border question “but there are other ways”.