In the UK you could be beaking the 1988 copyright act. Every writer has the right not to have their work subjected to 'derogatory treatment".

Also you would be creating an unauthorised arrangement of a copyright work if you used sections of the tune and words. However, if its for performence purposes only then a blind eye will usually be turned to a fair game parody. However, the author/composer would be entitled to any performing/record royalty fee for your adapation of his work - as it is counted as being his whole work, even if you set new lyrics to it. Unless you have entered into an agreement for a share and that has been notified to PRS/MCPS (uk wise).

In theory the writer could stop you performing the song altogether, although this is difficult in practice.