Pport issue..help please?

ok here it is.. my mother is in the uk since 2006.. she is not a citizen of uk but.she is working there.she went there as a nurse!! last yr she give her pport to the home office like 1 1/2 year ago to renew her visa. she has her work permit( which is i think unfortunately going to expire soon).. till now she didnt get back her pport. for the past 1 1/2 yr she is without one.. she's been contacting them since long.all they say is that they are working on it.. she even hired solicitors to deal with it..in vain..one solicitor after the other with no results but only with bills to pay afterward.. is there something fishy going on???? any reason y they are not giving back the passport.. if she were illegal , they would have deported her since long.so wats the problem???? can any1 help me plz? can advice or idea..thanks