Welcome to GoY. A photo would be helpful to make identifying the damage easier. Are you sure the cause is insects? Is it a pot plant or grown out doors? Is it pot bound? It could be cold draughts or under watering or moving it to a new location if its in a pot. It could be caused by disease or poor light .

Thanks for your reply I did send a picture but used the screen prior to actually registering, hopefully this error will not cause too much confusion.1

The tree is in a pot and has been kept in unheated conservatory during winter, it is during these periods that most damage occurs, We have put plant out this week as new leaves are appearing on damaged stems. It seems less prone to damge whilst outside. We have seen some spider webs but spiders are very small. we did try spraying but this had no effect on damage.Finally some not all leaves sometimes have a sticky substance on them.

Spider webs? Small spiders or tiny/minute spiders? Are they spidermite, dust sized specs with webs in the leaf internodes?

Sticky substance is probably caused by aphids or more likely scale insects, Check under the leaves (the ones still on the plant;-)) and look for the little monsters and crush them with your finger nail or spray with systemic insecticide. Wipe off the sticky residue with water or sooty mould can develop.
Probably not a good idea to keep a citrus in a unheated location in our winter.
For a more in depth answer try bonsaitreeforums.com in their citrus forum, that is if our members cannot help you further.
I hope this helps. If it didn't at least it gave you something to read.

Thanks for your help I will do as you suggest and hopefully will be able to cure the problem.