The Nigerian frontman signed for the Magpies just last summer for £10million, but new boss Sam Allardyce was shocked to discover a similar clause in Martins' contract to that of strike partner Michael Owen, according to The Evening Chronicle.
Owen could quit the club if someone offers £9million for his services, leaving Allardyce in the nightmare position of not knowing if his top two strikers will be at the club for the beginning of next season.
Martins recently said he was happy at Newcastle, but the north-east newspaper claims Arsenal will make a move if they lose Thierry Henry.
It is also reported that the club wanted to remove the clause from his contract after an impressive spell mid-season, but that would have meant ripping up his £60,000-a-week deal and giving him a new one.
The 23-year-old scored 17 goals in his debut season for the club after his big-money move from Inter Milan.