Hi Prachi,
This can be done with the Force.com Migration Tool: http://wiki.developerforce.com/page/Force.com_Migration_Tool
See the full documentation here: http://wiki.developerforce.com/page/Force.com_Migration_Tool
The tool can create or delete any meta-data that can be created through the Force.com IDE or Change Sets. It comes with a sample config file that contains example deployments for deploying objects and Apex code and deleting them as well. The documentation has a very detailed step-by-step guide here: http://www.salesforce.com/us/developer/docs/daas/index_Left.htm#StartTopic=Content/forcemigrationtool.htm
Thanks