The young midfielder was a surprise departure from Leeds on Monday evening, taking up a temporary contract at the Withdean Stadium which runs until January 3, but Johnson is in no doubt that he will see out the remainder of the three-and-a-half year contract he agreed with United in January.

Leeds paid around £250,000 to sign Johnson from Northampton Town at the turn of the year, and the 21-year-old became a first-team regular towards the end of last season, playing in all three of United's play-off fixtures.

His involvement this season has been more limited and after injuring his back two weeks before the term began, Johnson has started only one match with United's senior side against Bristol Rovers at the end of August.

Leeds accepted an approach to sign him from Brighton manager Micky Adams earlier this week, and Johnson marked his debut for Albion by scoring twice in their impressive 3-2 win over Leicester City on Tuesday night.

But the midfielder has no plans to forego a long-term career at Elland Road, saying: "I've got another two years on my contract after this season and I want to see them out.

"If anything, I'll be aiming to win a new contract at some stage and make sure I'm there for even longer. Leeds was a long-term move in my eyes and I'll be back to fight for my place in January. That's where I see myself staying.

"I'm a bit surprised that I haven't been more involved this season and my back injury didn't help. The other players have done well and picked up a lot of points, and it's difficult to break into a winning team.

"It got to the point where I wasn't close to a place on the bench so I went to see the manager to ask if I could go out on loan and get some first-team football. He agreed and it made sense to go to Brighton when they came in for me.

"Micky Adams knows me well because he was interested in me in January, and the squad down here is good. They play the same sort of passing football as Leeds and that's important for me because it means I'll get a lot out of the move. Their style suits mine. In the next two months I've got to get match fit and put in consistent performances so that when I go back to Leeds, Brighton will be able to say I've done a good job for them and I'll be ready to fight for a shirt."

McAllister was always certain to have more midfielders in his squad than midfield places available in his side this season, and the emergence of Fabian Delph as a first-team regular has heightened the competition for positions at the expense of players like Johnson.

McAllister said: "We've simply got too many midfield players and Bradley's down the pecking order so he needs to go out and get some football.

"We've got an abundance of left-footed midfielders as well, and I suppose the emergence of Fabian has pushed Bradley further down."