McNair sidefooted his fifth goal of the season from Rudy Gestede's square pass after the home side gave the ball away in their own half to boost Boro's hopes of avoiding relegation.

Goalkeeper Dejan Stojanovic beat away an Andre Green shot as Lee Bowyer's Addicks strove for an equaliser.

The debutant also denied Deji Oshilaja and Macaulay Bonne after the break as Charlton suffered a costly defeat which dropped them into the bottom three.

The win lifted Middlesbrough up three places to 19th in the table, to put them two points clear of their opponents in 22nd.

Charlton had Darren Pratley back in midfield after a month out with a back problem, but went into the game with a poor record against Boro of nine defeats and only one win the last 12 meetings between the teams.

Green was a busy presence in attack in the first half, but the visitors carried the greater threat, with Gestede just inches away from a second goal as he stretched to try and reach McNair's ball across the box.

Charlton's Lyle Taylor was booked for simulation after the break, when home fans were convinced it should have been a penalty after he went down in the box.

But they could not find a way past Stojanovic, signed from Swiss football in January, who went down well to save Oshilaja's header, then kept out Bonne's flick at the near post.

Middlesbrough's Lewis Wing forced a superb left-handed stop from Dillion Phillips with a low drive at the other end before Bonne headed Charlton's final opportunity over the bar in added time.

Charlton Athletic manager Lee Bowyer:

"I'm frustrated and disappointed again. We can't keep gifting teams goals.

"We are not good enough to give teams one-goal leads.

"We had three clear-cut chances. We have got to take at least one of them.

"The message to supporters is this - just stick together. We have got nine games to go and we have to keep fighting together."

Middlesbrough boss Jonathan Woodgate told BBC Radio Tees:

"The performance was absolutely outstanding. I thought there could have been two or three more goals.

"I can't pick out any players, I thought they were all terrific.

"We are in a dogfight and we have got to keep on fighting.

"Don't think that because we produced the goods against Charlton that that's it."