The 53-year-old former Celtic, Coventry and Southampton manager left with Boro languishing in 20th place in the npower Championship table having taken just 11 points from as many games to date this season.

Chairman Steve Gibson confirmed Strachan's departure by mutual consent live on BBC Radio Tees this evening.

He said: "It's a sad day. Gordon worked very hard for the football club.

"He would be the first to admit that things haven't turned out as we would have hoped.

"We have had some hard, long, very honest discussions in the last month, and today Gordon met with me mid-morning.

"We had a long discussion and during that debate, he offered his resignation and I accepted it."

Strachan, who signed a deal amounting to almost four years, has left the club without asking for a penny in compensation.

Gibson said: "Gordon is a very rare guy. He is better for knowing. I like him enormously, but it just hasn't worked and we had to face up to it.

"The integrity he has shown, he made life very easy for me. Not only did he offer his resignation, but in doing so, he tore up his contract.

"He sought no compensation, he walked away from the club with empty hands, and it's a measure of the man."

Former Middlesbrough defender Tony Mowbray is the fans' favourite to succeed Strachan, but as Gibson launches a search for a fourth manager in four and a half years, he is looking at a range of options.

Gibson said: "I am not going to talk about specifics. To concentrate on one individual wouldn't be the wisest thing to do.

"There is a list, and since the rumours broke about Gordon, I have got agents putting forward all sorts of names.

"I have been in football a long time and I know a lot of people in the game, so we will see what happens.

"It's not going to be something we will rush into."

Speculation over the former Manchester United midfielder's future has been circulating for several weeks, and that grew today when Strachan cancelled his pre-match press conference, although the official reason was that he was ill.

The Scot was appointed as successor to Gareth Southgate on October 26 last year, with chairman Gibson deciding a change was needed despite the team lying in fourth place in the Championship table and only a point behind then leaders West Brom.

But they finished the campaign 40 points worse off than eventual champions Newcastle and eight behind sixth-placed Blackpool, who went on to win the play-off final.

Boro were installed as pre-season favourites to win promotion back to the Barclays Premier League this time around, but head into tomorrow night's clash with Nottingham Forest 16 points adrift of current leaders QPR and seven shy of the play-off places.

Strachan managed only 13 victories in his 46-match reign despite an extensive overhaul of the squad, funded in part by the £8million sale of Adam Johnson to Manchester City, which saw him repeatedly head back across the border to snap up signings.

The addition of the likes of Barry Robson, Kris Boyd, Scott McDonald and Stephen McManus, all men with fine reputations in Scotland, failed to pay the dividends which the manager had hoped for.

Saturday evening's 2-1 home defeat by Leeds, which was played in front of a season's best crowd of 23,550 at the Riverside Stadium, proved the final straw.

Disgruntled fans made their feelings known on the final whistle, although they have been doing much the same for a large percentage of the campaign with many having been calling for another change at the top for some time.

Strachan never endeared himself to the supporters with his unique brand of public relations which, although sometimes mildly amusing, was more often obstructive and counter-productive and did little to enhance the reputation of a club fighting to win back fans amid dwindling attendances.

His tongue-in-cheek suggestion in a radio interview following the 2-2 draw with Portsmouth that he would "take drugs, and drink and smoke" to cope with the pressure went too far for some.

Those who responded to a recent survey conducted by the town's evening newspaper, the Evening Gazette, delivered a damning verdict on the manager's performance.

Coach Steve Agnew - the former Sunderland and Barnsley midfielder - has been put in temporary charge of the team, and will lead them from the dug-out against Forest tomorrow.