The High Court has ordered Mr Martin be duly elected as a senator for Tasmania to fill the vacancy left by Ms Lambie, after she discovered she held dual citizenship.
The order was made on Friday morning despite reports Mr Martin had been dumped by the Jacqui Lambie Network this week over a "lack of commitment".
But Justice Geoffrey Nettle said Ms Lambie should have brought forward any challenge to Ms Martin's election much earlier.
"There is no appearance (in court) on behalf of Ms Lambie or any evidence in support of what is said to have happened in the press," Justice Nettle told the court, sitting in Melbourne.
"It has not been established that Mr Martin has ceased to be a member of the Jacqui Lambie Network party.
"It is declared that Steve Martin be duly elected as a senator for the state of Tasmania."
The High Court also ordered that former Liberal minister Richard Colbeck replace the party's ousted speaker Stephen Parry, who was disqualified over dual citizenship.
Mr Martin and Mr Colbeck are expected to be sworn into the Senate in Canberra on Monday.
