The club's hopes of securing an automatic promotion place have faded thanks to a poor run of form and Harris, whose Millwall side have capitalised on Leeds' slump, has attributed their slide to an 'unsettling' January thanks to events surrounding Beckford.
Related ArticlesLeeds' fall, rise and fall againLeeds players 'must raise their game'Grayson warning to Leeds after Millwall defeatLeeds 0 Millwall 2Leeds title challenge 'back with a vengeance'Sport on television'First of all,' Harris said, 'He is a fantastic goalscorer. He has a talent to score goals and he has done it regularly over the last couple of years. He will move into the Premier League at the end of the season. There is no doubting that.
'But obviously what has happened around his January transfer request has not only unsettled him but it has unsettled the whole squad. That is either down to the individual but it is certainly down to the club as well and how they have handled it.
'That brings on pressure for the lad and the team itself. When you have got a goalscorer who is scoring nigh on every game it makes it easier all over the pitch because you know he will pop up with a goal at some stage.
'You take that out of the equation you then start panicking thinking well we have to keep a clean sheet maybe to get a point. If we let a goal in are we going to nick one at the other end? If Jermaine is not scoring then who is going to score the goals? It affects the whole set-up of the whole team and the squad.'
Beckford finally withdrew his transfer request to focus on his team's promotion push but he is now being tipped to move to Everton at the end of the season as a free agent when his contract expires.
He has 27 goals to his credit this season but has scored just five league goals since his winner knocked Manchester United out of the FA Cup at Old Trafford.
Some Leeds supporters have turned on Beckford who was booed by fans when he was substituted during the 2-0 defeat of Southend last weekend at Elland Road.
Leeds manager Simon Grayson will take his third-placed team to Carlisle on Tuesday night aiming to revive their hopes of securing automatic promotion place, although League One leaders Norwich and second-placed Millwall are favourites to go up.
Harris, whose team head to Yeovil on Tuesday, believes that pressure could have taken its toll on Leeds who were beaten 2-0 by Millwall last month.
'After Boxing Day think they were 21 points clear of us so it shows the run we have been but the demise they have had recently,' Harris added.
'They are the same bunch of players but they are playing without confidence. They have had a couple of wins so they will be a bit more positive.
'But pressure is a huge factor and when you play at a club like Leeds you are under pressure week in week out to win matches.
'Leeds fans and I had it at Nottingham Forest they expect you to be at the top of the league and above everybody else because they are a bigger club.'