No, there has been legislation since 2000 that says that part-time workers are entitled to the same terms and conditions and benefits of employment as full-time workers if they do the same or similar job (see full details click here).
You need to talk to your employer and ask them if there is a difference in your pay. If you do not get an answer that makes you happy they you can complain to them in writing; by law they need to reply to you within 21 days stating the reasons for any differences in the way they treat you compared to full-time staff.
You should get advice from a Trade Union official (if you are a member of the union), or contact Citizens Advice (www.citizensadvice.org.uk) or ACAS (www.acas.org.uk).
Image by Mr. Greenjeans