Hey
@Lakshmi,
Welcome to the forum! I know that you have directed your question at Jess, but I thought that it might be helpful to give you a response from my point of view too. This may well differ from Jess's, however, I think it is always useful to hear what a couple of people think.
Personally, I think that it is important to be cautious here. Graduate Recruitment is a very small world* and you want to start your training contract on a positive note with your firm. You also don't want to stress later on about the possibility of either firm finding out that you either reneged on a TC offer, or completed a vacation scheme having accepted a TC at a different firm. TCs are obviously notoriously difficult to get, and being left in the position of not having a training contract would be really awful given the position that you are currently in (although I think that this is unlikely, it is always possible if Firm A wished to retract the offer). My worry would be that, although it is not explicitly prohibited, it might be regarded as deceptive to complete a vacation scheme at a different firm once you have accepted.
For what it's worth, I do think that you should take as many opportunities as you can. Firm B's vacation scheme is definitely an opportunity that you shouldn't pass up lightly(!). However, my concern is that if you were to accept and complete the vacation scheme at Firm B, someone at Firm A might find out and this would reflect badly on you (and might even risk your TC offer). By being transparent you are demonstrating that you have integrity and that you value honesty (which can only be a good thing). I think asking the firm is also a mature response to a difficult situation. The firm should also appreciate that there are undoubtedly positives for you as an aspiring lawyer of completing more than one vacation scheme (not least for skills development). It also avoids tainting your relationship with Firm A in the future (if you were to renege on your TC after completing a vacation scheme without their knowledge at Firm B).
If I were in your position, I would be transparent with Firm A. I would tell them who Firm B is, tell them about the situation and give them reasons as to why I wanted to complete a vacation scheme at Firm B. Strong reasons to justify this might include: money (for example, if it were a 2 week vacation scheme, you might tell the firm that earning £800+ would allow you to travel/pay off your student loan etc.), personal/professional development (through expanding your network and giving you exposure to a range of legal tasks) and/or that it would allow me to make a more informed decision (by allowing me to experience more than one firm!). I would then ask whether they would consider extending the date on which my offer expired. I would also make clear that I would be more than happy to discuss it with them further on a call and that I was letting them know to be transparent and that you have no intention of being deceptive/dishonest.
This approach is bold, but I think it demonstrates maturity. I would make clear to Firm A that this was not a reflection of my attitude towards their offer or the prospect of training with them. It is important to demonstrate that you are not simply wishing to keep them on the hook in the hope of obtaining a better offer, but that it is a request driven by thoroughly considered reasoning.
Do let me know if you would like any further help with this
@Lakshmi. I appreciate that this is a tricky situation!
* Just as an example of Graduate Recruitment being a very small world: I interviewed at Firm 1 but was unsuccessful. I had already applied to Firm 2 and obtained a vacation scheme with them. I had a post-interview feedback call with a member of Firm 1's Graduate Recruitment team, let's call them Y. Y was lovely and I actually wrote them a postcard to say thank you (as they went above and beyond in giving me my feedback). Fast forward a few months, I start my vacation scheme at Firm 2. By coincidence, Y had moved to Firm 2 in the interim(!). In fact, they had moved a week or so after our call, but I didn't know. Moral of the story: you never know who will end up where, especially in Graduate Recruitment!