The North-West outfit are said to have switched their attention to the 28-year-old, who dropped down the pecking order under manager Arsene Wenger last season.
On Monday, reports claimed that the Arsenal club captain has agreed in principle a deal with United worth around £100,000 per week.
"If he wants to play football, and an offer comes in from a club like Manchester United, then it's hard for the club to say, 'no, you can't go there, we want to sell you to a club in Italy or Spain'," Parlour told talkSPORT.
"He was doing the captain's notes last year in the Arsenal programme but not getting in the team. I can't see that changing anytime soon. He wants to play first team football."
Vermaelen has one year remaining on his contract at the Emirates.