progressively aggressive

Question
A small group walk together with our mix of dogs.  One has a cocker.  2 and half years, male, neutered.  Been with owner since pup.  Runs and barks at golden labs - but was attacked apparently by one when about 9months.  Over the last month, he now runs barking at approaching dogs - any breed!  The other day he did nip a lab.  He barks at dogs off the lead and on the lead.

The other day I went to get a prickly twig out of his hair (he knows me well and I have looked after him at my house before) and he tried to nip my hand.  And the other day, apparently, whilst on the lead, owner was talking to someone and he bit someone sitting close (but NOT the person talking to the owner).

Otherwise! He is happy, playful, obedient and always comes to call, good as gold with other dogs on our walk.  Owner has been trying diverting tactics so far.

I have read through your other questions and have, thank you, taken in some really useful information.    We know this has to be stopped, but not quite sure of the approach!  Also it seems to be suddenly getting worse.  (I have owned and am used to dogs, this is my friends first dog, and I wouldn't presume to advise her! she is great with her dog, but not at all firm). Thank you.

Answer
Your friend needs a trainer...badly.  This is escalating and has to be stopped.  Diversion is not the answer.  The fact is he's getting away with it and IS going to bite someone seriously.

The first thing I'd do is soft-muzzle him on walks.  A soft muzzle allows him to pant, even drink but he can't nip or bark.  He has to learn to accept the muzzle so the first day or two you put it on..instantly take it off..praise & reward.  Then extend the time a bit.
You can't just stick it on him and expect him to be happy :)

She should take him with her to the pet store and make sure she gets the right size, etc...adjustable ones are best.

If she's in denial that things are going to a bad place, perhaps your group needs to say "it's training and a muzzle or we have to exclude you".  This dog tried to bite you..has bitten someone else.  This is serious.  Offer to go with her & the pup.

And this dog should NEVER be off leash.  That's being totally irresponsible.
Delores