The 19-year-old defender has enjoyed a meteoric rise this season and was watched by Everton manager Roberto Martinez during the 2-2 draw with Hibernian on Sunday.
Robertson moved to Tannadice from Scottish League Two side Queen's Park last summer and has since forced his way into the Scotland Under-21 picture.
"It's a compliment if anything if someone like Roberto Martinez comes to watch some of our young players," McNamara told Sky Sports News. "There is a lot of speculation at the moment, which we are just having to get used to.
"We have had no bids for any of our players. We have had a couple of phone calls and some enquiries but that's as far as it has gone.
"Andrew just joined us last summer. He is only 19-years-old and has just had six months with us. I think how he's done since he has joined us has been fantastic.
"I genuinely think the best thing would be for him to stay with us at least until the summer and continue to learn and enjoy his football.
"I speak to all the young lads about the speculation and when a bid comes in I will inform them of that. At the moment, I am trying to get them focused on winning matches for Dundee United."
United were on an impressive run of form before Christmas, scoring 22 goals in six matches, but three straight defeats over the festive period brought a swift reality check.
McNamara takes his side to Inverness this weekend grateful that they were able to stop the rot against Hibernian.
"The three defeats before the Hibs game were disappointing, certain things went against us," he added. "But great credit to the lads for the way they came back from 2-0 down and to get the draw was a good feeling.
"Inverness this weekend will be another tough test. It's a difficult place to go up in the Highlands with a new manager, John Hughes, who I worked with at Falkirk. I've got a lot of respect for him. We know what to expect.
"They have decent players and are very physical. We have to make sure we are up for the challenge and can impose our game."
You can watch Dundee United's game at Inverness from 12.30 this Sunday, 12 January on Sky Sports 3.