The attitude of the ruling group councillors to party discipline is the key issue here, not so much the fact there's a huge majority.
If there is very strong group discipline, you may have a problem. If dissent is allowed / encouraged within the group then you don't have an issue, assuming your scrutiny members are vocal and are willing to buck the party line (this is especially true of the committee chair).
The way to find this out (if you don't already know) would be to speak to senior officers in confidence about it. If you find that discipline is very tight, there may be one or two things you can do to make things a bit more challenging:
- Make a big effort in formulating the committee work programme - don't just garner the views of scrutiny committee members, you'll just get the ruling group orthodoxy - go further afield if you can. Speak to voluntary and community organisations to hear their concerns. Speak to senior officers to hear about the big issues facing the area. Try to get a picture of what is actually going on 'out there'. If members accept the topics raised by external bodies (which they should), they will at least be working to an agenda other than their party group's.
- Try to emphasise in your discussions with the members the importance of scrutiny being non-party political. Obviously don't browbeat them, but if you repeat this often enough it may start to sink in. There are some good publications on this site that you can use to make your case. Bring in examples of good practice from elsewhere to emphasise the positive role that good scrutiny can play, but draw attention to the non-party political way of working in the given authority.
- Bring the committee chair along to the CfPS conference this year to help reinforce your point
- In a sense, excessive group loyalty might only really hamper the 'holding to account' role of overview and scrutiny, i.e. members might be loathe to challenge the leadership of their group directly in full committee session. However, this doesn't necessarily prevent scrutiny from reviewing services and making useful recommendations. Just be aware that any glaring omissions unearthed by scrutiny may not be well received (by the scrutiny committee itself and/or the executive), but less contentious recommendations that arent embarssing to the ruling group will probably still be accepted and implemented.
I hope this helps. I can recommend Steve Leach's publication 'Party Politcs and Scrutiny in Local Government: Clearing the Hurdles', which is available on this site and may be of use.
Drop me an email if you need any further guidance: firstname.lastname@example.org