Epsom MP John Banks tried to use Prime Minister John Key's name on his own election hoardings last year - but was foiled when the Electoral Commission ruled it would require National's approval.
The Electoral Commission's advisory opinions show Mr Banks sent in four possible hoardings - all of which used Mr Key's name - in a bid to enhance his chances of winning the seat.
In a letter, Mr Banks told the commission his preferred hoarding was: "A vote for me/ Helps John Key. John Banks Epsom."
Other options included "A vote for me helps a John Key Govt" and "Strategic voting helps John Key. Vote John Banks in Epsom".
Mr Banks had argued that the use of Mr Key's name was not an advertisement for Mr Key or National because Mr Key was not a candidate in the electorate and there was no reference to the National Party.