not being offered job as electrician.

i am an apprentice electrician working for a large company in london. i have been told by my employer that i will not be offered a contract as an electrician when i qualifiy. they have told me that the reason for this is because of a diminishing work load,lack of new sites opening and the possibility of redundancies. they have told me that they are unable to offer me a position as an electrician yet they continue to use agency labour(some of which are unqualified to do the work) and sub work out to sub contractors on nearly every job. they have recently acquired two new contracts and have at least five currently running. surely they can not say they are unbale to offer me a position as an electrician purely because of a lack of work when they continue to use agency labour. if there was such a lack of work would they not be forced to stop the use of agency labour? i am aware they are not obligated to offer me a job after i qualify but i think the reasons they have given for not doing so do not hold true. i would be greatful to know where i stand legally. thanks.

Nowhere. As you said, they don't have to offer you a job. What their reasons for that are, and whether they are true or not, are irrelevant.