Thanks for your contributions everyone :). This is my first post and I guess I've learnt that I need to be more selective about the terminology i use. I don't think that the term 'best friends' accurately conveys the sort of relationship I'm thinking of. As some of you have suggested I'm thinking more of a close relationship than of a 'best friend' relationship to the exclusion of my kids having friends their own age. I'm not looking to shirk parenting responsibilities or shy away from disciplining my children when necessary and i'm sure there will be times during the teenage years that i'll be happy with merely being on speaking terms with them, lol. (Sirboobalot I like your sense of humour here 
). I'd like my children to have a circle of friends or 'best friend' their own age as they grow up. I guess what I'm trying to say is that in addition to all that I want them to know that they can always come to me with any problem they might have and be open with me.
On reflection, the question I want to ask is: " what qualities in a mum facilitate a great mother- child relationship in the long term?"
I thought that asking people who consider their mum to be their best friend would be a good place to start since they would obviously have a close relationship with their mother.
Wouldbeharrietvane - I think you've made an important point about parents accepting their children for who they are. It's pretty difficult to be close to someone who doesn't accept you for who you are.
Doodledumdums- lucky you, you sound like you have a great relationship with your mum :) I think you've made an insightful point re: fear of judgement and disappointment. I definately think that fear of being judged or of causing disappointment can build barriers to your children wanting to confide in you.
Emmyloo2- why do you think you are incredibly close to your mum? What is it about her that makes it easier for you to be close to her?
Ballroom blitz and scarred pierced- I think you've both made a very interesting point about your mum not being a friend but a parent growing up, and only now that you're an adult yourself do you see her as a friend as well as a parent. I guess that I too want my children to see me more as a parent whilst they are still young, but I'm hoping that if I do a good enough job of parenting they'll come to think of me as a friend (i.e someone they choose to be around just for the pleasure of my company) as well as a parent (someone to turn to for support and guidance) as they mature and have families of their own.
In my opinion a good parent possesses many of the same qualities you'd look for in a good friend; I.e. trustworthiness, supportive, understanding, someone who has your best interests at heart and cares about you. I guess the major distinction is that parents have a responsibility to their child that friends don't. I suppose to a certain extent I've answered my own question here..... but I'd still like to hear your views about how a parent can foster a great relationship with their kids over the longer term. Balancingfigure- you're right; when all is said and done you can't force your kids to be close to you, but I do believe that with mindful parenting you can avoid putting up barriers to them being close to you.