Shearer turned down the opportunity to assist Keegan at St James’ Park but is fully behind the ex-England manager and dismissed suggestions his job could be under threat should things not improve.

“I still believe and maintain they won’t go down,” said the Magpies’ record goalscorer.

“They need a result on Monday against Birmingham, because it has been a long time since they won.

“They have three crucial home games against (fellow relegation candidates) Fulham, Reading and Sunderland – and we will know more after those.

“It [speculation about Keegan’s future] is nonsense, but no one can stop that until they actually go out and get results.

“Winning matches changes everything; it stops people being negative about the club and the players.

“He [Keegan] knew what he was going into, and I am convinced – and I’m sure he is – that they will turn it around.”

Shearer believes Keegan’s position is secure.

“I don’t see any reason how he can be in danger,” he added.

“The owner and chairman have put their faith in Kevin.

“He is – and was – the right choice and he will take the club forward providing the owner gives him the funds. There is no point in appointing him if they are not prepared to do that.

“I just give him my full backing and hope he will get it right.

“I think he went into it knowing they had a difficult run of fixtures and that confidence was at an all-time low. Put those two together, and it is bad situation.”

The availability of significant transfer funds in the summer is essential if Keegan is to make an impact, according to Shearer.

Millionaire owner Mike Ashley has already spent a vast amount acquiring the club and funding purchases by previous boss Sam Allardyce, but Keegan will need a huge injection of money at the end of the season.

“He knows he has to get players in. He knows he has to get through this season, and then the owner will back him up in the summer with cash,” said Shearer.

“It needs a team that is going to have some confidence, because that can give you an extra 30-35%.”

Shearer also offered support to his one-time England strike partner Michael Owen, who has scored just three times – one coming in the FA Cup – since mid-October.

“Michael is confident, and you wouldn’t expect him to say anything different,” Shearer told Radio 5 Live’s Sportsweek programme.

“They have to believe they will be all right, and certainly he does.

“I believe in him. I know he missed chances against Blackburn [Newcastle’s last home match] – but if you give him chances against most teams he will score goals.”